Pyrano [3,2-d]-1,3-dioxin-8 ones

ABSTRACT

A novel 3-hydroxypyridin-4-one compound of formula I is provided                    
     wherein 
     R is hydrogen or a group that is removed by metabolism in vivo to provide the free hydroxy compound, 
     R 1  is an aliphatic hydrocarbon group or an aliphatic hydrocarbon group substituted by a hydroxy group or a carboxylic acid ester, sulpho acid ester or a C 1-6  alkoxy, C 6 -aryloxy or C 7-10 aralkoxy ether thereof, 
     R 3  is selected from hydrogen and C 1-6  alkyl; 
     and R 4  is selected from hydrogen, C 1-6  alkyl and a group as described for R 2 ; 
     characterised in that 
     R 2  is selected from groups 
     (i) —CONH—R 5    
     (ii) —CH 2 NHCO—R 5    
     (iii) —SO 2 NH—R 5    
     (iv) —CH 2 NHSO 2 —R 5    
     (v) —CR 6 R 6 OR 7    
     (viii) —CONHCOR 5    
      wherein 
     R 5  is selected from hydrogen and optionally hydroxy, alkoxy, or aralkoxy substituted C 1-3  alkyl, aryl and C 7-13  aralkyl, 
     R 6  is independently selected from hydrogen, C 1-13  alkyl, aryl and C 7-13  aralkyl, 
     and R 7  is selected from hydrogen, C 1-13  alkyl, aryl and C 7-13  aralkyl or a pharmaceutically acceptable salt of any such compound 
     with the proviso that when R 7  is hydrogen, R 6  is not selected from aryl and with the proviso that the compound is not l-ethyl-2-(1′hydroxyethyl)-3-hydroxypyridin-4-one.

This application is a division of application Ser. No. 09/437,211, filed Nov. 10, 1999, now U.S. Pat. No. 6,335,353, and of Ser. No. 09/451,112, filed Nov. 30, 1999 which is a CIP of Ser. No. 09/437,211 now U.S. Pat. No. 6,335,353, the entire content of which is hereby incorporated by reference in this application and which is a continuation of PCT/GB98/01517 filed May 26, 1998.

The present invention relates to novel compounds having activity as orally active iron chelators, to pharmaceutical compositions containing these and to their use in treating disorders associated with iron distribution, particular disorders involving excess of iron and presence of iron dependent parasites.

Members of the hydroxypyridone class are well known for their ability to chelate iron in physiological environment and these have reported as useful in treating iron related disorders such as thalassaemia and, when complexed with iron, anaemia. For example, see U.S. Pat Nos. 4,840,958, 5,480,894 and Hider et al (1996) Acta Haematologica 95:6-12. By virtue of their low molecular weight and high affinity for iron (III) these compounds now provide the possibility of removing iron from iron overloaded patients with the hope of providing oral activity. Related compounds for such use are disclosed in U.S. Pat. No. 4,585,780 wherein the characteristics required for oral activity are discussed further.

Two particular compounds referred to by Hider et al, CP20 and CP94 (see Tables 1 and 2 herein), have proved to be effective in man, but both have disadvantages in that they are rapidly inactivated by phase II metabolism and are able to cross the placenta and blood brain barrier. The extensive biotransformation of these compounds is reflected by their limited ability to mobilise excess body iron in thalassaemic patients.

The requirements for orally active chelators are set out in Table 4 of Hider et al as (i) good absorption from the gastrointestinal tract, (ii) efficient liver extraction, (iii) poor entry into peripheral cells such as thymus, muscle, heart and bone marrow and (iv) poor ability to penetrate the blood-brain barrier and matemal/placental barriers. This reference refers to desired partition coefficients (K_(part)), herein referred to as distribution coefficient values (D_(pH7.4)), for these properties as (i) >0.2, (ii) >1.0, (iii) <0.001 and (iv) <0.001, respectively rendering one compound seemingly unsuited to satisfying all four criteria. Hider et suggest the pro-drug strategy to be one possible route forward but no specific compounds have so far been found to meet all criteria.

Pivalic acid esters of hydroxyalkyl substituted 3-hydroxypyridin-4-ones have been studied as pro-drugs and found to lead to efficient excretion of iron, in bile and urine, but as reported by Hider et al these are now thought to potentially interfere with the carritine cycle and thus may not be suitable for use in regular and/or large doses in man.

It is known that the 2-(1′-hydroxyethyl) metabolite of 1,2-diethyl-3-hydroxypyridin-4-one (CP94) produced in rat is an active iron chelator (see Singh et al (1992) Drug Metabolism and Disposition Vol 20. No 2, page 256-261). EP 0494754 A proposes 1-hydroxyethyl as one of many possible substituents at any of the pyridin-4-one positions 1, 2, 5 or 6 for use as iron chelator in treatment of malaria; none of these compounds are however exemplified as made or tested for activity. EP 0768302 A (Novartis) describes a series of related 3-hydroxypyridin-4-ones in which the 2-position is substituted by a methyl group which carries an optionally substituted phenyl or heteroyl ring and a free or esterified hydroxy group. The phenyl or heteroyl group is taught as an essential element of these compounds.

The present inventors now have provided a group of 3-hydroxypyridin-4-one iron chelators having improved properties as compared to the prior art as assessed against the criteria set out above. The preferred compounds of the invention are all characterised by meeting a further criterion (v) in so far as they have a pM for Iron III, i.e. affinity for iron as Fe III, of at least 20, preferably in excess of 23. Preferred compounds have efficiency of iron mobilisation of in excess of 52% when given orally to rats. The definition of pM used herein is the concentration of ferric ion in solution when the total amount of iron equals 10⁻⁶ M and the concentration of ligand is 10⁻⁵ M and pH is 7.4.

The present compounds offer the prospect of effective pharmaceutical formulations having reduced levels of active agent, with particular properties of selective targeting of the chelating activity to tissues where the iron level requires alteration, particularly the liver. A particular property of preferred compounds of the invention is that they are not significantly metabolised through conjugation and, in preferred forms, are provided as prodrugs.

Thus in a first aspect of the present invention there is provided a novel 3-hydroxypyridin-4-one compound of formula I

wherein

R is hydrogen or a group that is removed by metabolism in vivo to provide the free hydroxy compound,

R¹ is an aliphatic hydrocarbon group or an aliphatic hydrocarbon group substituted by a hydroxy group or a carboxylic acid ester, sulpho acid ester or a C₁₋₆ alkoxy or C₇₋₁₀aryloxy or aralkyloxy ether thereof,

R³ is selected from hydrogen and C₁₋₆ alkyl;

and R⁴ is selected from hydrogen, C₁₋₆ alkyl and a group as described for R²;

characterised in that

R² is selected from groups

(i) —CONH—R⁵

(ii) —CH₂NHCO—R⁵

(iii) —SO₂NH—R⁵

(iv) —CH₂NHSO₂—R⁵

(v) —CR⁶R⁶OR⁷

(viii) —CONHCOR⁵

 wherein

R⁵ is selected from hydrogen and optionally hydroxy, alkoxy, aryloxy or aralkoxy substituted C₁₋₁₃ alkyl, aryl and C₇₋₁₃ aralkyl,

R⁶ is independently selected at each occurrence from hydrogen, C₁₋₁₃ alkyl, aryl and C₇₋₁₃ aralkyl,

and R⁷ is selected from hydrogen, C₁₋₁₃ alkyl, aryl and C₇₋₁₃ aralkyl or a pharmaceutically acceptable salt of any such compound

with the proviso that when R⁷ is hydrogen, R⁶ is not selected from aryl.

and with the proviso that the compound is not 1-ethyl-2-(1′-hydroxyethyl)-3-hydroxypyrid-4-one.

Preferably at least one of R, R¹ or R⁷ is such as to form a 3-ester or ether prodrug. Those skilled in the art will recognise the term 3-ester or ether prodrug to mean compounds wherein the 3-hydroxy group has been esterified with a carboxylic or sulpho acid, or formed into an ether with a C₁₋₆ alkyl or C₁₋₁₀ aralkyl group which is removed in vivo to provide the free hydroxy compound. Typically such carboxylic acid esters or ethers are of C₁₋₇ type, ie. the 3-substituent is —O—R⁸ or —OC(O)—R⁸ where R⁸ is C₁₋₆ alkyl or C₁₋₁₀ arakyl.

More preferably R⁵ and R⁷ are independently selected from C₁₋₆ alkyl, aryl or aralkyl, e.g. benzyl, which may be substitued with C₁₋₆ alkoxy. More preferably R⁶is independently selected from hydrogen or C₁₋₆ alkyl.

The positions 5 and 6 are preferably unsubstituted, ie. R³ and R⁴ are preferably hydrogen, but may be substituted with conventional pyridin-4-one substituents as disclosed by the prior art as suitable in iron chelators.

Where R¹ is an aliphatic carbon group substituted by hydroxy and that hydroxy is esterified the ester acyl group is preferably of formula —CO—R⁹ where R⁹ is C₁₋₆ alkyl or C₁₋₁₀ aryl, more preferably being —CO-Phenyl or —CO-hetero, eg. heterocylic rings with one of two nitrogen members and three to five carbons.

R¹ and R⁵ are conveniently independently selected C₁₋₆ alkyl, preferably methyl or ethyl, but preferably may be a hydroxy, alkoxy or esterified hydroxy terminated C₁₋₆ alkyl group. Where R¹ is a hydroxy terminated alkyl it is advantageous that the alkyl group is of 3 to 6 carbons long, more preferably being 3 carbons long, e.g. where R¹ is —(CH₂)₃—OH, as such compounds are known to be metabolised in vivo to the corresponding —(CH₂)₂—CO₂H derivative with consequent advantages of low D_(pH7.4) after metabolism, e.g. in the liver.

Most preferred compounds are of the type where R² is of groups (i), or (v).

More preferably R² is a group —CR⁶R⁶OR⁷ wherein R⁶ is independently selected at each occurrence from hydrogen, C₁₋₁₃ alkyl or C₆ aryl and R⁷ is C₁₋₆ alkyl, more preferably methyl or ethyl. An alternate preferred group for R² is —CONH—R⁵.

Still more preferred compounds of the invention have a D_(pH7.4) as determined in an octanol/MOPS pH 7.4 system of in excess of 1, more preferably being metabolised in vivo to a metabolite having a D_(pH7.4) of less than 1, more preferably less than 0.1 and still more preferably less than 0.001, as set out in the criteria above.

A second aspect of the present invention provides processes for preparation of new compounds of the invention, a third provides novel intermediates for use in these processes, a fourth provides the use of the compounds in therapy, a fifth provides their use in manufacture of medicaments and a sixth provides pharmaceutical compositions comprising them.

The process of the invention is broadly that as set out in any one or more of Schemes 1, 2, 3 and 4. The preferred process comprises all relevant steps of these schemes for a given compound of the invention. Those skilled in the art will readily produce free compounds from the salts shown by conventional techniques.

Novel intermediates of the invention are of formula (IIb), (IIc) and (III) of Scheme 1 (IVa), (IVb) and (IVc) of Scheme 2, (VI), (VII) and (VIII) of Scheme 3 and (X), (XI), (XII) of Scheme 4.

Thus a first process of the invention comprises the reaction of a 2-(1′-hydroxyalkyl)-3-hydroxy-pyran-4(1H)-one of formula (IIa)

where R¹⁰ is a group as defined in R⁶

with benzaldehyde dimethyl acetal to provide the corresponding 8-oxo-4,8-dihydro-2-phenyl-4H[3,2-d]-m-dioxin of formula (IIb),

reacting that compound with a compound R¹NH₂ to give the corresponding pyridino dioxin of formula (IIc)

and reducing that with hydrogen to give the corresponding 2-hydroxyalkyl-pyridin-4(1H)-one.

A second process of the invention comprises the protection of the 3-hydroxyl group of a 2-(1′-hydroxyalkyl)-3-hydroxy-pyran4(1H)-one of formula (IV),

eg. using a benzyl halide, preferably benzyl bromide to give a compound (IVa)

alkylating the 2-(1′-hydroxy) group, eg. with an alkyl halide such as alkyl iodide to, reacting the product thereof (IVb)

with a compound R¹NH₂ to provide the corresponding 2-hydroxyalkyl-pyridin-4(1H)-one (IVc)

and reducing that to provide the correpsonding unprotected compound.

A third process of the present invention reacts a 2-carboxyl-3-benzoyloxy-pyran-4(1H)-one of formula (IXd), that optionally being provied by oxidising the corresponding formyl compound (IXc) eg. with sulfamic acid and sodium chlorite,

with mercaptothiazoline, eg. in the presence of dicyclocarbodiimide and dimethylaminopyridine to provide the corresponding 2-carbonyl-thiazolidine-2-thione of formula (X),

reacts that with a compound R⁵NH₂ to give the corresponding 2-amido compound of of formula (XI),

reacting that with a compound R¹NH₂ to give the corresponding 2-amido-pyridin-4(1H)-one compound of formula (XII)

and optionally reducing that to provide the corresponding 2-hydroxyalkyl-pyridin-4(1H)-one.

Novel intermediates are the 8-oxo-4,8-dihydro-2-phenyl4H[3,2-d]-m-dioxins, 2-(1-alkoxyoxyalkyl)-3-hydroxy-pyran4(1H)-ones and corresponding 2-carbonyl-thiazolidine-2-thiones corresponding to the compounds of Formula I.

Also provided within formula (I) are novel compounds which are metabolites of the preferred prodrug compounds of the first aspect of the invention but which have D_(pH7.4) less than 1; these also being active iron III chelating agents once the compounds of the first aspect have been metabolised eg. in the liver, to remove any ether or ester protecting group where that was required to provide a D_(pH7.4) of 1 or above. For example in compound CP362 below, the methyl group (R in formula I above), is removed in vivo resulting in a drop in D_(pH7.4) to give the compound of formula I wherein R is hydrogen, R² is CH(OH)CH₃, R¹ is ethyl and R³ and R⁴ are hydrogen. This compound 1-ethyl-2-(1′-hydroxyethyl)-3-hydroxypyrid4-one is known.

Those skilled in the art will readily appreciate that some of these compounds will be known already, but in so far as compounds are novel they are also rendered inventive by their relationship as active metabolites of the novel compounds of the first aspect. Particularly provided is the provision of such metabolites ‘for use in therapy’ eg. ‘for use in therapy of iron related disorders’. These compounds, while not of ideal D_(pH7.4) for oral activity, will still be of potential use by parenteral or other route of administration.

Salts of the compounds of the invention may readily be formed by reaction of the compound with the appropriate base or acid under suitable conditions. Zwitterionic forms, where appropriate, may conveniently be obtained by freeze drying an aqueous solution at a selected pH. Freeze drying of an aqueous solution whose pH has been adjusted to 7.0 or to greater than 9.0 with the desired base provides a convenient route to a salt of that base. Salts with acids may conveniently be obtained by recrystallization of the compound of formula (I) from an aqueous/organic solution, for example the hydrochloride being obtained on recrystallization from a dilute hydrochloric acid/ethanol solution.

Pro-drugs may be formed by reaction of any free hydroxy group compound of formula (I) or a derivative thereof with the appropriate reagent, in particular with an organic acid or derivative thereof, for example as described in U.S. Pat. No. 4,908,371 and/or with an alcohol or phenol, for example using standard esterification procedures.

The compounds of formula (I) may be formulated with a physiologically acceptable diluent or carrier for use as pharmaceuticals for veterinary, for example in a mammalian context, and particularly for human use, by a variety of methods. For instance, they may be applied as a composition incorporating a liquid diluent or carrier, for example an aqueous or oily solution, suspension or emulsion, which may often be employed in injectable form for parenteral administration and therefore may conveniently be sterile and pyrogen free. Oral administration is preferred for the preferred compounds of the invention. Although compositions for this purpose may, incorporate a liquid diluent or carrier, it is more usual to use a solid, for example a conventional solid carrier material such as starch, lactose, dextrin or magnesium stearate. Such solid compositions may conveniently be of a formed type, for example as tablets, capsules (including spansules), etc.

Other forms of administration than by injection or through the oral route may also be considered in both human and veterinary contexts, for example the use of suppositories or pessaries. Another form of pharanceutical composition is one for buccal or nasal administration, for example lozenges, nose drops or an aerosol spray. Thus, the invention further includes a pharmaceutical composition comprising a 3-hydroxypyridin-4-one drug or prodrug of formula (I) as defined hereinbefore together with a physiologically acceptable diluent or carrier.

Compositions may be formulated in unit dosage form, i.e. in the form of discrete portions each comprising a unit dose, or a multiple or sub-multiple of a unit dose. The dosage of active compound given will depend on various factors, including the particular compound employed in the composition and the mode of administration and type of disease be treated, eg. whether for iron overload as in thalessemia or for use in treating iron dependent parasites eg. malaria.

Typical dosages for use in human therapy will usually lie in the region of about 0.1 to 50 g daily, preferably 0.5 g to 20 g daily, particularly from about 1 or 2 g to 10 or 15 g daily, for example about 5 g, veterinary doses being on a similar g/kg body weight ratio. However, it will be appreciated that it may be appropriate under certain circumstances to give daily dosages either below or above these levels. Where desired, more than one compound according to the present invention may be administered in the pharmaceutical composition, when the total dosage will usually correspond to those discussed above, or, indeed, other active compounds may be included in the composition.

The present invention will now be described by way of illustration only by reference to the following non-limiting Examples, Tables, Schemes and Figures. Further examples of the invention will occur to those skilled in the art in the light of these.

Tables

Table 1: shows compound codes, structures, D_(pH7.4) (also known as Kpart), pKa, Logβ3, pM and in vivo iron mobilisation data for compounds of the invention where R² is of type (v), both active agents for oral administration and their metabolites, the latter being suitable for parenteral or other non-oral route administration.

Table 2: summarises Table 1 with significant pKa2 and comparative data added.

Table 3: shows compound codes structures, D_(pH) _(7.4) (also known as Kpart), pKa, Logβ3, pM and in vivo iron mobilisation data for compounds of the invention where R² is of type (i).

Schemes

Scheme 1 shows the reaction scheme for synthesis of novel intermediates from compounds of formula (IIa) to compounds of formula (III)

Scheme 2 shows the reaction-scheme for synthesis of novel intermediates from compounds (IV) to orally active compounds (V) and

Scheme 3 shows the reaction scheme for formation of R¹ ester type oral active compounds.

Scheme 4 shows the reaction scheme for synthesis of novel intermediates from compounds (IX) to amide products (XII) and (XIII).

FIGURES

FIG. 1 shows a speciation plot of ratio of ligand to Iron (III) v pH.

FIG. 2 shows in vivo iron mobilisation using the metabolite free hydroxy compounds of the invention.

FIG. 3 shows in vivo iron mobilisation using the orally active ether compounds of the invention.

Synthesis

Known Intermediates

2,5-Dihydro-2,5-dimethoxy-2-furanmethanol

Produced by the method of Achamatowicz et al (1971) Tetrahedron; 27: 1973-1996. Distillation at 78° C./0.5 mmHg (Lit. ^((a))71° C./1.0 mmHg; gave the title compound (177 g, 73.8%) as colorless liquid.

Evaporation of the solvent and distillation at 74° C./0.4 mmHg gave title product as colorless liquid. (115.5 g, 72.2%).

6-Methoxy-2H-pyran-3(6H)-one

Produced by the method of of Achamatowicz et al (1971). Distillation at 47˜48° C./0.5 mmHg (lit. 76˜81° C./13 mmHg) afforded a clear, sharp-smelling oil.

Novel Intermemiate

4-Bromo-6-methoxy-2H-pyran-3(6H)-one

To a solution of 6-methoxy-2H-pyran-3(6H)-one 12.8 (0.1 mole) in 40 ml CH₂Cl₂ at 0° C. was added 16.0 g (0.1 mole) of bromine in 10 ml of CH₂Cl₂. Then 14 ml of triethylamine was added dropwise at 0° C. and the reaction was allowed to warm to room temperature and stir for two hours. The reaction was then diluted with 200 ml of toluene. After filtration, the organic solution was then washed with 5% NaHCO₃ and brine, dried with Na₂SO₄, filtered and concentrated to yield the crude product as light brown solid Recrystallisation from ethyl acetate afforded the title compound (17 g, 82%) as a white crystalline solid. m.p. 74-75° C.

¹H-NMR (CDCl₃) δ: 3.5 (s, 3H, OCH₃), 4.4 (q, 2,2′-H, AB center, J₂₂.=14.5 Hz, δ₂₂.=18.5 Hz), 5.05 (d, 1H, 6-H), 7.25 (d, 1H, 5-H)

Anal. Calcd. for C₆H₇O₃Br: C, 34.81; H, 3.41%. Found: C, 35.03; H, 3.45%.

Recrystallisation from ethyl acetate afforded the title compound (17 g, 82%) as a white crystalline solid. m.p. 74-75° C.

Anal. Calcd. for C₆H₇O₃Br: C, 34.81; H, 3.41%. Found: C, 35.03; H, 3.45%.

Known Intermediates

3-Hydroxy-pyran-4(1lH)-one (pyromeconic acid)

The solid was treated with activated carbon and recrystallised from toluene to yield the title compound (2.5 g, 80%) as a light yellow plates. m.p. 114-115° C. [lit. 113-115.5° C. (Tate and Miller., 1964) U.S. Pat. No. 3,130,204].

6-Chloromethyl-3-hydroxy-pyran-4(1H)-one (chlorokojic acid)

The product was collected by filtration and washed with petroleum ether and then recrystallised from water to give the pure title compound (42.5 g, 75.9%) as colourless needles. m.p. 166-168° C. [lit. 166-167° C.: Tilbrook G Thesis Kings College London. 995].

3-Hydroxy-6-methyl-pyran-4(1H)-one (allomaltol)

Recrystallisation from isopropanol afforded 14.8 g (62.8%) of analytically pure allomaltol as colourless plates. m.p. 152-153° C. [lit. 152-153° C. Tibrooke G Thesis as above].

2-Hydroxymethyl-3-hydroxy-pyran-4(1H)-one (α-hydroxymaltol)

Sodium hydroxide (4 g, 100 mmol, 1.25 eq.) dissolved in 10 ml distalled water was added to a solution of 3-hydroxy-pyran-4(1H)-one (8.96 g, 80 mmol, 1 eq.) in 50 ml methanol and allowed to stir at room temperature for 5 minutes. 16 ml (200 mmol, 2.5 eq.) of 35% formaldehyde solution was added dropwise over 15 minutes and the solution was stirred overnight. After adjustment to pH 1 with 37% w/v hydrochloric acid, the reaction mixture was concentrated in vacuo to dryness and the resulting solid was extracted with 2×100 ml of isopropanol at 90° C. The isopropanol extracts were concentrated to yield the crude products. Recrystallisation from isopropanol afforded 9.7 g (85.4%) of the pure title product as a white crystalline solid. m.p. 154-156° C. [lit. 148-150° C. (Tate and Miller., 1964)].

¹H-NMR (DMSO-d₆) δ: 4.4 (s, 2H, 2-CH₂OH), 4.6-5.7 (br., 1H, 2-CH₂OH), 6.34 (d, 1H, 5-H), 8.1 (d, 1H, 6-H), 9.0 (br., s, 1H, 3-OH)

2-(1-Hydroxyethyl)-3-hydroxy-pyran-4(1H)-one

3-Hydroxy-pyran-4(1H)-one (5.6 g, 50 mmol, 1 eq.) was added to 50 ml water and the pH of the solution was adjusted to 10.5 using 50% aqueous sodium hydroxide. Acetaldehyde (2.64 g, 60 mmol, 1.25 eq.) dissolved in 20 ml water was slowly added dropwise over 1 hour and the solution allowed to stir overnight. The reaction mixture was acidified to pH 1 with 37% w/v hydrochloric acid and concentrated in vacuo to dryness. The residue was extracted with 2×70 ml of isopropanol at 90° C. The isopropanol extracts were combined and concentrated to yield after recrystallisation from toluene, the pure product (3.7 g, 47.4%) as a pale yellow crystalline solid. m.p. 131-132° C. [lit. 130-131° C. (Ichimoto, 1970)].

¹H-NMR (DMSO-d₆) δ: 1.3 (d, 3H, 2-CHCH₃), 5.03 (q, 1H, 2-CHCH₃), 6.38 (d, 1H, 5-H), 8.2 (d, 1H, 6-H)

2-Hydroxymethyl-3-hydroxy-6-methyl-pyran-4(1H)-one

Allomaltol (12.6 g, 100 mmol, 1 eq.) was added to an aqueous solution containing 4.4 g (110 mmol, 1.1 eq.) of sodium hydroxide in 100 ml distilled water and stirred at room temperature for 5 minutes. 9 ml (110 mmol, 1.1 eq.) of 35% w/v formaldehyde solution was added dropwise over 10 minutes and the solution allowed to stir overnight. Acidification to pH 1 using concentrated hydrochloric acid and cooling to 3-5° C. for 12 hours gave a crystalline deposit. The title product was isolated by filtration as colourless needles (12.8 g, 82%). m.p. 159-161° C. [lit. (1): 157-158° C.; lit. (2): 161-163° C.]. Tilbrook (1993) Recrystrallisation solvent ethanol.

¹H-NMR (DMSO-d₆) δ: 2.30 (s, 3H, 6-CH₃), 4.5 (s, 2H, 2-CH₂OH), 4.6-5.7 (br., 1H, 2-CH₂OH), 6.25 (s, 1H, 5-H), 8.7-9.2 (br., 1H, 3-OH)

2-(1-Hydroxyethyl)-3-hydroxy-6-methyl-pyran-4(1H)-one

Allomaltol (12.6 g, 100 mmol, 1 eq.) was added to 100 ml water and the pH of the solution was adjusted to 10.5 using 50% aqueous sodium hydroxides. Acetaldehyde (5.5 g, 125 mmol, 1.25 eq.) dissolved in 25 ml water was slowly added dropwise over 1 hour and the solution allowed to stir overnight. After adjustment to pH 1 with 37% hydrochloric acid, the reaction mixture was extracted with 3×150 ml of dichioromethane. The combined organic extracts were dried over anhydrous sodium sulphate, filtered and concentrated to yield the crude product. Recrystallisation from toluene afforded the pure product (14.1 g, 83%) as white needles. m.p. 127-130° C. [lit. 126-128° C.]. Ellis (1993)

¹H-NMR (DMSO-d₆) δ: 1.25 (d, 3H, 2-CHCH₃), 2.2 (s, 3H, 6-CH₃), 4.9 (q, 1H, 2-CHCH₃), 5.2 (br., s, 1H, 2-CHOH), 6.1 (s, 1H, 5-H), 8.6 (br., s, 1H, 3-OH)

2-(1-Hydroxypropyl)-3-hydroxy-6-methyl-pyran-4(1H)-one

Allomaltol (12.6 g, 100 nmmol, 1 eq.) was added to 100 ml water and the pH of the solution was adjusted to 10.5 using 50% aqueous sodium hydroxides. Propionaldehyde (8.1 g, 150 mmol, 1.5 eq.) dissolved in 50 ml methanol was slowly added dropwise over 1 hour and the solution allowed to stir at room temperature for 48 hours. After adjustment to pH 1 with 37% hydrochloric acid, the reaction mixture was evaporated to dryness and the residue taken up into 300 ml of dichloromethane. The organic layer was washed with water (150 ml), dried over anhydrous sodium sulphate, filtered and concentrated to yield the crude product. Recrystallisation from toluene afforded the pure product (14.5 g, 78.9%) as a white crystalline solid. m.p. 134-136° C. [lit. 132-135° C. Ellis (1993)].

¹H-NMR (CDCl₃) δ: 1.12 (t, 3H, 2-CHCH₂CH₃), 1.7-2.3 (m, 2H, 2-CHCH₂CH₃), 2.45 (s, 3H, 6-CH₃), 4.95 (q, 1H, 2-CHCH₂CH₃), 5.0-6.0 (br., 1H, 2-CHOH), 6.3 (s, 1H, 5-H)

Novel Intermediates

EXAMPLE 1 8-Oxo4,8-dihydro-2-phenyl-4H-pyrano[3,2-d]-m-dioxin

A solution of 2-hydroxymethyl-3-hydroxy-pyran-4(1H)-one (2.84 g, 20 mmol, 1 eq.), benzaldehyde dimethyl acetal (6.08 g, 40 mmol, 2 eq.) and toluene-p-sulphonic acid monohydrate (0.04 g, cat.) in 50 ml DMF was rotated under aspirator pressure at 80° C. for 3 hours. The solvent was removed under high vacuum, the residue taken up into 100 ml dichloromethane. The organic solution was washed successively with aqueous Na₂CO₃ and brine. After drying over magnesium sulphate, the solvent was removed to give the crude product. Recrystallisation from CH₂Cl₂/Pet. ether 40/60 afforded the pure title compound (3.77 g, 82%) as a white crystalline solid. m.p. 141-143° C.

¹H-NMR (CDCl₃) δ: 4.72 (d, 2H, CH₂O), 5.88 (s, 1H, CHPh), 6.35 (d, 1H, 7-H(pyranone)), 7.2-7.9 (m, 6H, Ar & 6-H(pyranone))

Anal. Calcd. for C₁₃H₁₀O₄: C, 67.82; H, 4.38%. Found: C, 68.13; H, 4.26%.

EXAMPLE 2 8-Oxo4,8-dihydro4-methyl-2-phenyl-4H-pyrano[3,2-d]-m-dioxin

In an analogous procedure in the preparation of 8-oxo-4,8-dihydro-2-phenyl4H-pyrano[3,2-d]-m-dioxin using 2-(1-hydroxyethyl)-3-hydroxy-pyran-4(1H)-one yielded the crude product. Purification by column chromatography on silica gel (eluant: EtOAc) furnished the title compound after recrystallisation from EtOAc/Pet. ether 40/60, as a white crystalline solid (yield=84.5%). m.p. 112-113° C.

¹H-NMR (CDCl₃) δ: 0.55 (d, 3H, CHCH₃), 5.0 (q, 1H, CHCH₃), 5.8 (s, 1H, CHPh), 6.25 (d, 1H, 7-H(pyranone)), 7.1-7.75 (m, 6H, Ar & 6-H(pyranone))

Anal. Calcd. for C₁₄H₁₂O₄: C, 68.85; H, 4.95%. Found: C, 68.63; H, 4.86%.

EXAMPLE 3 8-Oxo4,8-dihydro-6-methyl-2-phenyl-4H-pyrano[3,2-d]-m-dioxin

In an analogous procedure in the preparation of 8-oxo-4,8-dihydro-2-phenyl4H-pyrano[3,2-d]-m-dioxin using 2-hydroxymethyl-3-hydroxy-6-methyl-pyran-4(1H)-one afforded the title compound (Yield=82.1%) after recrystallisation from EtOAc/Pet. ether 40/60, as a white crystalline solid; m.p. 91-94° C.

1H-NMR (CDCl₃) δ: 2.25 (s, 3H, 6-CH₃), 4.75 (d, 2H, CH₂O), 5.9 (s, 1H, CHPh), 6.18 (s, 1H, 7-H(pyranone)), 7.2-7.8 (m, 5H, Ar)

Anal. Calcd. for C,₁₄H,₁₂O₄: C, 68.85; H, 4.95%. Found: C, 68.63; H, 4.86%

EXAMPLE 4 8-Oxo-4,8-dihydro-4,6-dimethyl-2-phenyl4H-pyrano[3,2-d]-m-dioxin

In an analogous procedure in the preparation of 8-oxo-4,8-dihydro-2-phenyl4H-pyrano[3,2-d]-m-dioxin using 2-(1-hydroxyethyl)-3-hydroxy-6-methyl-pyran-4(1H)-one yielded the crude product. Purification by column chromatography on silica gel (eluant: EtOAc) furnished the title compound after recrystallisation from EtOAc/Pet. ether 40/60, as a white crystalline solid (yield=86.7%). m.p. 120-122° C.

¹H-NMR (CDCl₃) δ: 1.6 (d, 3H, CHCH₃), 2.25 (s, 3H, 6-CH₃), 5.08 (q, 1H, CHCH₃), 5.9 (s, 1H, CHPh), 6.18 (s, 1H, 7-H(pyranone)), 7.2-7.8 (m, 5H, Ar)

Anal. Calcd. for C₁₅H_(14 O) ₄: C, 69.76; H, 5.46%. Found: C, 69.94; H, 5.67%.

EXAMPLE 5 8-Oxo-4,8-dihydro-4-ethyl-6-methyl-2-phenyl-4H-pyrano[3,2-d]-m-dioxin

In an analogous procedure in the preparation of 8-oxo-4,8-dihydro-2-phenyl4H-pyrano[3,2-d]-m-dioxin using 2-(1-hydroxyproyl)-3-hydroxy-6-methyl-pyran-4(1H)-one afforded the title compound after recrystallisation from EtOAc/Pet. ether 40/60, as a white crystalline solid (Yield=61.3%); m.p. 111-114° C.

¹H-NMR (CDCl₃) δ: 1.0 (t, 3H, CHCH₂CH₃), 1.6-2.1 (m, 2H, CHCH₂CH₃), 2.2 (s, 3H, 6-CH₃), 4.7-5.0 (m, 1H, CHCH₂CH₃), 5.8 (s, 1H, CHPh), 6.1 (s, 1H, 7-H(pyranone)), 7.15-7.7 (m, 5H, Ar)

Anal. Calcd. for C,₁₆H₁₆O₄: C, 70.58; H, 4.92%. Found: C, 70.35; H, 4.89%.

2-Hydroxymethyl-3-benzyloxy-6-methyl-pyran-4(1H)-one (Known)

Sodium hydroxide (4.84 g, 121 mmuol, 1.1 eq.) dissolved in 10 ml distilled water was added to 100 ml methanol containing 2-hydroxymethyl-3-hydroxy-6-methyl-pyran-4(1H)-one ((17.2 g, 110 mmol, 1 eq.) and heated to reflux. Benzyl bromide (20.7 g, 121 mmol, 1 eq.) was added dropwise over 30 minutes and then refluxed overnight. The reaction mixture was concentrated in vacua, the residue taken up into 300 ml dichloromethane and the inorganic salts filtered off. The dichloromethane layer was washed with 2×100 ml 5% w/v sodium hydroxide solution, 100 ml water, dried (Na₂SO₄), and concentrated in vacuo to yield the crude product as a yellow crystalline solid. Recrystallisation from CH₂Cl₂/Pet. ether 40/60 afforded the title product in 80% yield (21.6 g) as a white crystalline solid. m.p. 115-116° C. [lit. 114-116° C. Tilbrook (1995)].

1H-NMR (CDCl₃) δ: 2.2 (s, 3H, 6-CH₃), 2.6 (br., s, 1H, 2-CH₂OH), 4.3 (br., s, 2H, 2-CH₂OH), 5.18 (s, 2H, CH₂Ph), 6.16 (s, 1H, 5-H(pyranone)), 7.4 (s, 5H, Ar)

Novel Intermediates and Orally Active Prodrugs of the Invention

EXAMPLE 6 2-(1-Hydroxyethyl)-3-benzyloxy-6-methyl-pyran-4(1H)-one

The title compound was prepared by the method outlined for 2-hydroxymethyl-3-benzyloxy-6-methyl-pyran-4(1 )-one, using 8.5 g (50 mmol, 1 eq.) of 2(1-hydroxyethyl)-3-hydroxy-6-methyl-pyran-4(1H)-one and 9.5 g benzyl bromide (55 mmol, 1.1 eq.) to yield the pure product 10.1 g (77.7%) after recrystallisation from CH₂Cl₂/Pet. ether 40/60, as a white crystalline solid. m.p 91-92° C.

¹H-NMR (CDCl₃) δ: 1.25 (d, 3H, 2-CHCH₃), 2.25 (s, 3H, 6-CH₃), 2.55 (br., s, 1H, 2-CHOH), 4.9 (q, 1H, 2-CHCH₃), 5.18 (s, 2H, CH₂Ph), 6.16 (s, 1H, 5-H (pyranone)), 7.4 (s, 5H, Ar)

EXAMPLE 7 2-(1′-Hydroxypropyl)-3-benzyloxy-6-methyl-pyran-4(1H)-one

The title compound was prepared by the method outlined for 2-hydroxymethyl-3-benzyloxy-6-methyl-pyran-4(1H)-one, using 7.36 g (40 mmol, 1 eq.) of 2-(1-hydroxypropyl)-3-hydroxy-6-methyl-pyran-4(1H)-one and 7.5 g benzyl bromide (44 mmol, 1.1 eq.) to yield the pure product 8.9 g (81.2%) after recrystallisation from CH₂Cl₂/Pet. ether 40/60, as a white crystalline solid. m.p. 88-89° C.

¹H-NMR (CDCl₃) δ: 0.8 (t, 3H, 2-CHCH₂CH₃), 1.2-1.9 (m, 2H, 2-CHCH ₂CH₃), 2.2 (s, 3H, 6-CH₃), 2.4 (br., s, 1H, 2-CHOH), 4.5 (t, 1H, 2-CHCH₂CH₃), 5.08 (s, 2H, CH₂Ph), 6.04 (s, 1H, 5-H(pyranone)), 7.28 (s, 5H, Ar)

2-Hydroxymethyl-3-benzyloxy-pyran-4(1H)-one (known)

The title compound was prepared by the method outlined for 2-hydroxymethyl-3-benzyloxy-6-methyl-pyran-4(1H)-one, using 7.1 g (50 mmol, 1 eq.) of 2-hydroxymethyl-3-hydroxy-pyran-4(1 H)-one and 9.5 g benzyl bromide (55 mmol, 1.1 eq.) to yield the crude product as an organe oil. Further purification by column chromatography on silica gel (eluant: 10% CH₃OH/90% CHCl₃) furnished the pure product (9.4 g, 81%) as a bright yellow oil. (Looker and Clifton (1986).

¹H-NMR (CDCl₃) δ: 1.8 (br., s, 1H, 2-CH₂OH), 4.4 (br., s, 2H, 2-CH₂OH), 5.18 (s, 2H, CH₂Ph), 6.35 (d, 1H, 5-H(pyranone)), 7.4 (s, 5H, Ar), 7.65 (d, 1H, 6-H(pyranone))

EXAMPLE 8 2-(1′-Hydroxyethyl)-3-benzyloxy-pyran-4(1H)-one

The title compound was prepared by the method outlined for 2-hydroxymethyl-3-benzyloxy-6-methyl-pyran-4(1H)-one, using 4.68 g (30 mmol, 1 eq.) of 2-(1-hydroxyethyl)-3-hydroxy-pyran-4(1H)-one and 5.64 g benzyl bromide (33 mmol, 1.1 eq.) to yield the pure product 6.1 g (82%) after recrystallisation from CH₂Cl₂/Pet. ether 40/60, as a white crystalline solid. m.p. 97-100° C.

¹H-NMR (CDCl₃) δ: 1.35 (d, 3H, 2-CHCH₃), 2.5 (br., s, 1H, 2-CHOH), 4.95 (q, 1H, 2-CHCH₃), 5.21 (s, 2H, CH₂Ph), 6.38 (d, 1H, 5-H(pyranone)), 7.4 (s, 5H, Ar), 7.7 (d, 1H, 6-H(pyranone))

Orally Active Prodrugs of the Invention

EXAMPLE 9 2-Metboxymethyl-3-benzyloxy-6-methyl-pyran-4(1H)-one

To a suspension of sodium hydride (0.48 g, 20 mmol, 2 eq.) in 30 ml dry DMF was added 2-hydroxymethyl-3-benzyloxy-6-methyl-pyran-4(1H)-one (2.46 g, 10 mmol, 1 eq.) followed by dropwise addition of iodomethane (4.26 g, 30 mmol, 3 eq.) at 0° C. under nitrogen. After stirring for 30 minutes at this temperature, the reaction mixture was poured into ice cold water (100 ml) and extracted with dichloromethane (3×50 ml). The combined organic fractions were dried over anhydrous sodium sulphate, filtered and concentrated in vacuo to yield the crude product (2.6 g, ˜100%) as an orange oil which solidified on cooling. Recrystallisation from CH₂Cl₂/Pet. ether 40/60 afforded the pure product (2.35 g, 90%) as a white crystalline solid. m.p. 30-32° C.

¹H-NMR (CDCl₃) δ: 2.25 (s, 3H, 6-CH₃), 3.26 (s, 3H, OCH₃), 4.2 (s, 2H, 2-CH₂OCH₃), 5.18 (s, 2H, CH₂Ph), 6.16 (s, 1H, 5-H(pyranone)), 7.35 (s, 5H, Ar)

EXAMPLE 10 2-(1-Methoxyethyl)-3-benzyloxy-6-methyl-pyran-4(1H)-one

In an analogous procedure in the preparation of 2-methoxymethyl-3-benzyloxy-6-methyl-pyran-4(1H)-one using 2-(1-hydroxyethyl)-3-benzyloxy-6-methyl-pyran-4(1H)-one (2.6 g, 10 mmol, 1 eq.) yielded the title compound as an orange oil (2.65 g, 97%). Further purification by column chromatography on silica gel (eluant: EtOAc) furnished the pure product as a bright yellow oil.

¹H-NMR (CDCl₃) δ: 1.18 (d, 3H, 2-CHCH₃), 2.25 (s, 3H, 6-CH₃), 3.1 (s, 3H, OCH₃), 4.5 (q, 1H, 2-CHCH₃), 5.2 (s, 2H, CH₂Ph), 6.16 (s, 1H, 5-H(pyranone)), 7.4 (s, 5H, Ar).

EXAMPLE 11 2-(1′-Methoxypropyl)-3-benzyloxy-6-methyl-pyran-4(1H)-one

In an analogous procedure in the preparation of 2-methoxymethyl-3-benzyloxy-6-methyl-pyran-4(1H)-one using 2-(1-hydroxypropyl)-3-benzyloxy-6-methyl-pyran-4(1H)-one (5.48 g, 20 mmol, 1 eq.) yielded the title compound (5.2 g, 90.3%) as an orange oil which solidified on cooling. Recrystallisation from CH₂Cl₂/Pet. ether 40/60 afforded the pure product as a white crystalline solid. m.p. 63-65° C.

¹H-NMR (CDCl₃) δ: 0.9 (t, 3H, 2-CHCH₂CH₃), 1.2-1.8 (m, 2H, 2-CHCH₂CH₃), 2.34 (s, 3H, 6-CH₃), 3.18 (s, 3H, OCH₃), 4.3 (t, 1H, 2-CHCH₂CH₃), 5.24 (s, 2H, CH₂Ph), 6.2 (s, 1H, 5-H(pyranone)), 7.38 (s, 5H, Ar)

EXAMPLE 12 2-Methoxymethyl-3-benzyloxy-pyran-4(1H)-one

In an analogous procedure in the preparation of 2-methoxymethyl-3-benzyloxy-6-methyl-pyran-4( 1H)-one using 2-hydroxymethyl-3-benzyloxy-pyran-4( 1 H)-one (2.32 g, 10 mmol, 1 eq.) yielded the title compound as an orange oil (2.5 g, ˜100%). Further purification by column chromatography on silica gel (eluant: EtOAc) furnished the pure product as a bright yellow oil.

¹H-NMR (CDCl₃) δ: 3.25 (s, 3H, OCH₃), 4.3 (s, 2H, 2-CH₂OCH₃), 5.2 (s, 2H, CH₂Ph), 6.3 (d, 1H, 5-H(pyranone)), 7.3 (s, 5H, Ar), 7.65 (d, 1H, 6-H (pyranone))

EXAMPLE 13 2-(1-Methoxyethyl)-3-benzyloxy-pyran-4(1H)-one

In an analogous procedure in the preparation of 2-methoxymethyl-3-benzyloxy-6-methyl-pyran-4(1H)-one using 2-(1-hydroxyethyl)-3-benzyloxy-pyran-4(1H)-one (2.46 g, 10 mmol, 1 eq.) yielded the title compound as a yellow oil (2.4 g, 92.3%). Further purification by column chromatography on silica gel (eluant: EtOAc) furnished the pure product (2.1 g, 80.8%) as a bright yellow oil.

¹H-NMR (CDCl₃) δ: 1.18 (d, 3H, 2-CHCH₃), 3.1 (s, 3H, OCH₃), 4.45 (q, 1H, 2-CHCH₃), 5.2 (s, 2H, CH₂Ph), 6.3 (d, 1H, 5-H(pyranone)), 7.3 (s, 5H, Ar), 7.65 (d, 1H, 6-H(pyranone))

EXAMPLE 14 2-(1-Ethoxyethyl)-3-benzyloxy-6-methyl-pyran-4(1H)-one

In an analogous procedure in the preparation of 2-methoxymethyl-3-benzyloxy-6-methyl-pyran-4(1 H)-one using 2-(1-hydroxyethyl)-3-benzyloxy-6-methyl-pyran-4(1H)-one (5.2 g, 20 mmol, 1 eq.) and 9.36 g iodoethane (60 mmol, 3 eq.) yielded the title compound as an orange oil (5.4 g, 94% Crude). Further purification by column chromatography on silica gel (eluant: EtOAc) furnished the pure product as a bright yellow oil.

¹H-NMR (CDCl₃) δ: 1.05-1.65 (m, 6H, 2-CHCH₃& OCH₂CH₃), 2.38 (s, 3H, 6-CH₃), 3.3 (q, 2H, OCH₂CH₃), 4.65 (q, 1H, 2-CHCH₃), 5.25 (s, 2H, CH₂Ph), 6.2 (s, 1H, 5-H(pyranone)), 7.4 (s, 5H, Ar)

Novel Intermediates of the Invention

EXAMPLE 15 8-Oxo-4,8-dihydro-2-phenyl-5-methyl-4H-pyridino[3,2-d]-m-dioxin

To a solution of 8-oxo-4,8-dihydro-2-phenyl-4H-pyrano[3,2-d]-m-dioxin (2.3 g, 10 mmol, 1 eq.) in ethanol (10 ml)/water (10 ml) was added 2.5 ml (20 mmol, 2 eq.) of 40% aqueous methylamine followed by 2N sodium hydroxide solution until pH 12.5 was obtained. The reaction mixture was sealed in a thick-walled glass tube and stirred at 70° C. for 3 hours. After adjustment to pH 1 with concentrated hydrochloric acid, the solvent was removed by rotary evaporation prior to addition of water (50 ml) and washing with diethyl ether (3×50 ml). Subsequent adjustment of the aqueous fraction to pH 7 with 10N sodium hydroxide solution was followed by extraction into dichloromethane, (4×50 ml), the combined organic layers then being dried over anhydrous soditum sulphate, filtered, rotary evaporated to give a yellow solid. Recrystallisation from methanol/diethyl ether afforded the pure product (1.6 g, 65.8%) as a light yellow crystalline solid. m.p. 210-211° C.

¹H-NMR (DMSO-d₆) δ: 3.55 (s, 3H, N—CH₃), 5.08 (s, 2H, CH₂O), 5.92 (s, 1H, CHPh), 6.12 (d, 1H, 7-H(pyridinone)), 7.25-7.85 (m, 6H, Ar & 6-H(pyridinone))

EXAMPLE 16 8-Oxo-4,3-dihydro-2-phenyl-5,6-dimethyl-4H-pyridino[3,2-d]-m-dioxin

In an analogous procedure in the preparation of 8-oxo-4,8-dihydro-2-phenyl-5-methyl-4H-pyridino[3,2-d]-m-dioxin using 8-oxo-4,8-dihydro-6-methyl-2-phenyl-4H-pyrano[3,2d]-m-Dioxin (1.22 g, 5 mmol) yielded the title compound as a white powder (0.85 g, 66%/). m.p. 256-258° C.

1H-NMR (rnethanol-d₄) δ: 2.2 (s, 3H, 6-CH₃), 3.35 (s, 3H, N—CH₃), 4.95 (s, 2H, CH₂O), 5.8 (s, 1H, CHPh), 6.5 (s, 1H, 7-H(pyridinone)), 7.0-7.5 (m, 5H, Ar)

EXAMPLE 17 8-Oxo-4,8-dihydro-2-phenyl-4,5,6-trimethyl-4H-pyridino[3,2-d]-m-dioxin

In an analogous procedure in the preparation of 8-oxo-4,8-dihydro-2-phenyl-5-methyl-4H-pyridino[3,2-d]-m-dioxin using 8-oxo-4,8-dihydro-4,6-dimethyl-2-phenyl-4H-pyrano-[3,2-d]-m-dioxin (2.58 g, 10 mmol) yielded the crude product. Further purification by column chromatography on silica gel (eluant: 20% CH₃OH/80% CHC₃) afforded the pure title compound (1.54 g, 56.8%) after recrystallisation from methaol/diethyl ether as a pale yellow crystalline solid m.p. 199-201° C.

¹H-NMR (DMSO-d₆) δ: 1.7 (dd, 3H, CHCH₃), 2.35 (s, 3H, 6-CH₃), [3.44 (s, isomer B) & 3.5 (s, isomer A); 3H, N—CH₃], 4.9-5.4 (m, 1H, CHCH₃), [5.75 (s, isomer A) & 6.05 (s, isomer B); 1H, CHPh], 6.35 (s, 1H, 7-H(pyridinone)), 7.2-7.9 (m, 5H, Ar)

EXAMPLE 18 8-Oxo-4,8-dihydro-2-phenyl-4-ethyl-5,6-dimethyl-4H-pyridino[3,2-d]-m-dioxin

In an analogous procedure in the preparation of 8-oxo-4,8-dihydro-2-phenyl-5-methyl4H-pyridino[3,2-d]-m-dioxin using 8-oxo-4,8dihydro-4ethyl-6-methyl-2-phenyl4H-pyrano[3,2-d]-m-dioxin (4.08 g, 15 mmol) yielded the crude product. Further purification by column chromatography on silica gel (eluant: 20% CH₃OH/80% CHCl₃) afforded the pure title compound (1.7 g, 39.8%) after recrystallisation from CHCl₃/diethyl ether as a pale yellow crystalline solid. m.p. 185-187° C.

¹H-NMR (DMSO-d₆) δ: 0.8-1.4 (m, 3H, CHCH₂CH₃), 1.5-2.2 (m, 2H, CHCH₂CH₃), 2.3 (s, 3H, 6-CH₃), [3.38 (s, isomer B) & 3.45 (s, isomer A); 3H, N—CH₃], [4.5-4.8 (m, isomer B) & 4.9-5.4 (m, isomer A); 1H, CHCH₂CH₃], [5.68 (s, isomer A) & 5.95 (s, isomer B); 1H, CHPh], 6.25 (s, 1H, 7-H (pyridinone)), 7.2-7.8 (m, 5H, Ar)

EXAMPLE 19 8-Oxo-4,8-dihydro-2-phenyl-4-methyl-5-ethyl-4H-pyridino[3,2-d]-m-dioxin

To a solution of 8-oxo-4,8-dihydro-4-methyl-2-phenyl-4H-pyrano[3,2-d]-m-dioxin (1.7 g, 7 mmol, 1 eq.) in ethanol (10 ml)/water (10 ml) was added 1.2 ml (14 mmol, 2 eq.) of 70% aqueous ethylamine followed by 2N sodium hydroxide solution until pH 12.5 was obtained. The reaction mixture was sealed in a thick-walled glass tube and stirred at 70° C. for 3 hours. After removal the solvent, the residue was purified by column chromatography on silica gel (eluant: 15% CH₃OH/85% CHCl₃) to afford the title product (1.5 g, 79.1%) as a yellow oil.

¹H-NMR (CDCl₃) δ: 1.2-2.2 (m, 6H, CHCH₃& N—CH₂CH₃), 3.4-4.0 (m, 2H, N—CH₂CH₃), 4.8-5.4 (m, 1H, CHCH₃), [5.6 (s, isomer A) & 6.0 (s, isomer B); 1H, CHPh], 6.3 (d, 1H, 7-H(pyridinone)), 7.0-7.7 (m, 6H, Ar & 6-H(pyridinone)).

EXAMPLE 20 8-Oxo-4,8-dihydro-2-phenyl-5-(3-hydroxypropyl)-4H-pyridino[3,2-d]-m-dioxin

To a solution of 8-oxo-4,8-dihydro-2-phenyl-4H-pyrano[3,2-d]-m-dioxin (3.45 g, 15 mmol, 1 eq.) in ethanol (50 ml)/water (50 ml) was added 3-hydroxypropylamine (2.25 g, 30 mmol, 2 eq.) followed by 2N sodium hydroxide solution until pH 12.5 was obtained. The reaction mixture was refluxed for 3 hours. TLC analysis (10% CH₃OH/90% CHCl₃) showed that no starting material was present. After removal of solvent by rotary evaporation, the residue was purified by column chromatography on silica gel (eluant: 20% CH₃OH/80% CHCl₃) to afford the title compound (3.35 g, 77.8%) as a yellow crystalline solid m.p. 73-76° C.

¹H-NMR (CDCl₃) δ: 1.5-2.1 (m, 2H, N—CH₂CH₂CH₂O), 3.2-4.0 (m, 4H, N—CH₂CH₂CH₂O), 4.0-5.2 (b,r., 1H, OH), 4.8 (s, 2H, CH₂O), 5.7 (s, 1H, CHPh), 6.2 (d, 1H, 7-H(pyridinone)), 7.0-7.8 (m, 6H, Ar & 6-H(pyridinone))

EXAMPLE 21 8-Oxo-4,8-dihydro-2-phenyl-4-methyl-5-(3-hydroxypropyl)-4H-pyridino[3,2-d]-m-dioxin

In an analogous procedure in the preparation of 8-oxo-4,8-dihydro-2-phenyl-5-(3-hydroxypropyl)-4H-pyridino[3,2-d]-m-dioxin using 8-oxo-4,8-dihydro-4-methyl-2-phenyl-4H-pyrano[3,2-d]-m-dioxin (1.83 g, 7.5 mmol, 1 eq.) yielded the title compound (1.3 g, 57.6%) after purification by column chromatography on silica gel (eluant: 20% CH₃OH/80% CHCl₃) as a yellow oil.

¹H-NMR (CDCl₃) δ: 1.5 (d, 3H, CHCH₃), 1.5-2.1 (m, 2H, N—CH₂CH₂CH₂O), 3.2-4.0 (m, 4H, N—CH₂CH₂CH₂O), 4.0-5.2 (br., 1H, OH), 5.28 (q, 1H, CHCH₃), 5.58 (s, 1H, CHPh), 6.2 (d, 1H, 7-H(pyridinone)), 7.0-7.8 (m, 6H, Ar & 6-H (pyridinone))

EXAMPLE 22 8-Oxo-4,8-dihydro-2-phenyl-5[(3-benzoyfoxy)propyl]-4H-pyridino[3,2-d]-m-dioxin

A solution of triphenyl phosphine (3.46 g, 13.2 mmol, 1.1 eq.) and 8-oxo-4,8-dihydro-2-phenyl-5-(3-hydroxypropyl)-4H-pyridino[3,2-d]-m-dioxin (3.3 g, 12 mmol, 1 eq.) in dry tetrahydrofuran (100 ml) was added dropwise to a solution of diethyl azodicarboxylate (2.3 g, 13.2 mmol, 1.1 eq.) and benzoic acid (1.5 g, 12 mmol, 1 eq.) in dry tetrahydrofuran (30 ml) at room temperature. After stirring the mixture overnight at room temperature, the solvent was removed under reduced pressure. The residue thus obtained was purified by column chromatography on silica gel (eluant: 12% CH₃OH/88% CHCl₃) to afford the title compound (4.1g, 89.7%) as a light yellow oil.

¹H-NMR (CDCl₃) δ: 1.95-2.55 (m, 2H, N—CH₂CH₂CH₂O), 3.82 (t, 2H, N—CH₂CH₂CH₂O), 4.34 (t, 2H, N—CH₂CH₂CH₂O), 4.9 (s, 2H, CH₂O), 5.8 (s, 1H, CHPh), 6.3 (d, 1H, 7-H(pyridinone)), 7.0-8.2 (m, l 11H, Ar & 6-H (pyridinone)).

Orally Active Prodrugs of the Invention

EXAMPLE 23 1,6-Dimethyl-2-methoxymethyl-3-benzyloxy-pyridin-4(1H)-one hydrochloride

To a solution of 2-methoxymethyl-3-benzyloxy-6-methyl-pyran-4(1H)-one (3.12 g, 12 mmol, 1 eq.) in ethanol (10 ml)/water (10 ml) was added 2.8 g (36 mmol, 3 eq.) of 40% aqueous methylarnine followed by 2N sodium hydroxide solution until pH 13 was obtained. The reaction mixture was sealed in a thick-walled glass tube and stirred at 70° C. for 12 hours. After adjustment to pH 1 with concentrated hydrochloric acid, the solvent was removed by rotary evaporation prior to addition of water (50 ml) and washing with diethyl ether (3×50 ml). Subsequent adjustment of the aqueous fraction to pH 7 with 10N sodium hydroxide solution was followed by extraction into dichloromethane (4×50 ml), the combined organic layers then being dried over anhydrous sodium sulphate, filtered and the solvent removed in vacuo. The residue was redissolved in 30 ml methanol and adjusted to pH 1 with concentrated hydrochloric acid. The solution was reconcentrated-in vacuo to yield the crude product. Recrystallization from methanol/diethyl ether gave the pure title compound (3.05 g, 82%) as a white crystalline solid m.p. 125-128° C.

¹H-NMR (DMSO-d₆) δ: 2.6 (s, 3H, 6-CH₃), 3.26 (s, 3H, OCH₃), 3.86 (s, 3H, N—CH₃), 4.6 (s, 2H, 2-CH₂OCH₃), 5.04 (s, 2H, CH₂Ph), 5.5-6.5 (br., 1H, OH), 7.2-7.8 (m, 6H, Ar & 5-H(pyridinone))

EXAMPLE 24 1,6-Dimethyl-2-(1-methoxyethyl)-3-benzyloxy-pyridin-4(1H)-one hydrochloride

The title compound was prepared by the method outlined for 1,6-dimethyl-2-methoxy-methyl-3-benzyloxy-pyridin-4(1H)-one hydrochloride, using 3.56 g (13 mmol, 1 eq.) of 2-(1-methoxyethyl)-3-benzyloxy-6-methyl-pyran-4(1H)-one to yield the pure product 2.64 g (62.8%) after recrystallisation from methanol/diethyl ether, as a white crystalline solid m.p. 117-119° C.

¹H-NMR (DMSO-d₆) δ: 1.3 (d, 3H, CHCH₃), 2.54 (s, 3H, 6-CH₃), 3.04 (s, 3H, OCH₃), 3.96 (s, 3H, N—CH₃), 5.08 (s, 2H, CH₂Ph), 5.12 (q, 1H, CHCH3), 7.4 (s, 5H, Ar), 7.6 (s, 1H, 5-H(pyridinone))

EXAMPLE 25 1-Ethyl-2-methoxymethyl-3-benzyloxy-6-methyl-pyridin-4(1H)-one hydrochloride

The title compound was prepared by the method outlined for 1,6-dimethyl-2-methoxy-methyl-3-benyloxy-pyridin-4(1H)-one hydrochloride, using 6.5 g (25 mmol, 1 eq.) of 2(1-methoxymethyl)-3-benzyloxy-6-methyl-pyran-4(1H)-one and 4.82 g (75 mmol, 3 eq.) of 70% aqueous ethylamine to yield the pure product 3.7 g (45.7%) after recrystallisation from methanol/diethyl ether, as a white crystalline solid m.p. 114-116° C.

¹H-NMR (DMSO-d₆) δ: 1.3 (t, 3H, N—CH₂CH₃), 2.64 (s, 3H, 6-CH₃), 3.27 (s, 3H, OCH₃), 4.35 (q, 2H, N—CH₂CH₃), 4.6 (s, 2H, 2-CH₂OCH₃) 5.1 (s, 2H, CH₂Ph), 6.0-7.0 (br., 1H, OH), 7.45 (s, 5H, Ar), 7.52 (s, 1H, 5-H (pyridinone))

EXAMPLE 26 1-Ethyl-2-methoxymethyl-3-benzyloxy-pyridin4(1H)-one

To a solution of 2-methoxymethyl-3-benzyloxy-pyran-4(1H)-one (2.46 g, 10 mmol, 1 eq.) in ethanol (10 ml)/water (10 ml) was added 1.93 g (30 mmol, 3 eq.) of 70% aqueous ethylamine followed by 2N sodium hydroxide solution until pH 13 was obtained. The reaction mixture was sealed in a thick-walled glass tube and stirred at 70° C. overnight. After adjustment to pH 1 with concentrated hydrochloric acid, the solvent was removed by rotary evaporation prior to addition of water (50 ml) and washing with diethyl ether (3×50 ml). Subsequent adjustment of the aqueous fraction to pH 7 with 10N sodium hydroxide solution was followed by extraction into dichloromethane (4×50 ml), the combined organic layers then being dried over anhydrous sodium sulphate, filtered and the solvent removed in vacuo. The residue was purified by column chromatography on silica gel (eluant: 15% CH₃OH/85% CHCl₃) to afford the title compound (2.05 g, 75.1%) as a yellow oil.

¹H-NMR (CDCl₃) δ: 1.3 (t, 3H, N—CH₂CH₃), 3.24 (s, 3H, OCH₃), 3.95 (q, 2H, N—CH₂CH₃), 4.35 (s, 2H, 2-CH₂OCH₃), 5.25 (s, 2H,CH₂Ph), 6.45 (d, 1H, 5-H (pyridinone)), 7.15-7.6 (m, 6H, Ar & 5-H(pyridinone)).

EXAMPLE 27 1-Ethyl-2-(1-methoxyethyl)-3-benzyloxy-pyridin-4(1H)-one

In an analogous procedure in the preparation of 1-ethyl-2-methoxymethyl-3-benzyloxy-pyridin-4(1H)-one using 2-(1-methoxyethyl)-3-benzyloxy-pyran-4(1H)-one 3.12 g (12 mmol, 1 eq.) yielded the title compound (1.03 g, 29.6%) after purification by column chromatography on silica gel (eluant: 15% CH₃OH/85% CHCl₃) as a yellow oil.

¹H-NMR (CDCl₃) δ: 1.1-1.6 (m, 6H, CHCH₃ & N—CH₂CH₃), 3.0 (s, 3H, OCH₃), 4.1 (q, 2H, N—CH₂CH₃), 4.95 (q, 1H, CHCH₃), 5.18 (s, 2H, CH₂Ph), 6.3 (d, 1H, 5-H (pyridinone)), 7.0-7.5 (m, 6H, Ar & 5-H(pyridinone))

EXAMPLE 28 1,6-Dimethyl-2-(1-methoxypropyl)-3-benzyloxy-pyridin4(1H)-one

In an analogous procedure in the preparation of 1-ethyl-2-methoxymethyl-3-benzyloxy-pyridin-4( 1H)-one using 2-(1-methoxypropyl)-3-benzyloxy-6-methyl-pyran-4(1H)-one 4.32 g (15 mmol, 1 eq.) and 3.49 g (45 mmol, 3 eq.) of 40% aqueous methylamine yielded the title compound (1.7 g, 37.6%) after purification by column chromatography on silica gel (eluant: 15% CH₃OH/85% CHCl₃) as a yellow oil.

¹H-NMR (CDCl₃) δ: 0.9 (t, 3H, CHCH₂CH₃), 1.1-1.9 (m, 2H, CHCH₂CH₃), 2.3 (s, 3H, 6-CH₃), 3.05 (s, 3H, OCH₃), 3.65 (s, 3H, N—CH₃), 4.65-5.0 (m, 1H, CHCH₂CH₃), 5.24 (s, 2H, CH₂Ph), 6.3 (d, 1H, 5-H (pyridinone)), 7.1-7.6 (m, 6H, Ar)

EXAMPLE 29 1,6-Dimethyl-2-(1-ethoxymethyl)-3-benzyloxy-pyridin-4(1H)-one

In an analogous procedure in the preparation of 1-ethyl-2-methoxymethyl-3-benzyloxy-pyridin-4(1H)-one using 2-(1-ethoxymethyl)-3-benzyloxy-6-methyl-pyran-4(1H)-one 5.76 g (20 mmol, 1 eq.) and 4.65 g (60 mmol, 3 eq.) of 40% aqueous methylamine yielded the title compound (3.68 g, 61.1%) after purification by column chromatography on silica gel (eluant: 15% CH₃OH/85% CHCl₃) as a yellow oil.

¹H-NMR (CDCl₃) δ: 1.1-1.6 (m, 6H, CHCH₃ & OCH₂CH₃), 2.3 (s, 3H, 6-CH₃), 3.2 (q, 2H, OCH₂CH₃), 3.7 (s, 3H, N—CH₃), 5.2 (q, 1H, CHCH₃), 5.25 (s, 2H, CH₂Ph), 6.3 (s, 1H, 5-H(pyridinone)), 7.1-7.6 (m, 5H, Ar)

De-Alkylated Active Metabolites of Orally Active Compounds of the Invention

EXAMPLE 30 1-Methyl-2-hydroxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride

8-Oxo-4,8-dihydro-2-phenyl-5-methyl-4H-pyridino[3,2d]-m-dioxin (1.22 g, 5 mmol) was dissolved in 30 ml of ethanol and adjusted to pH 1 with concentrated hydrochloric acid prior to hydrogenolysis for 12 hours in the presence of 5% Pd/C catalyst (0.2 g). Filtration followed by rotary evaporation gave the crude product as a white solid. Recrystallization from methanol/diethyl ether gave the pure title compound (0.82 g, 86%) as a white crystalline solid. m.p. 157-159° C.

¹H-NMR (DMSO-d₆) δ: 4.18 (s, 3H, N—CH₃), 4.8 (s, 2H, 2-CH₂OH), 7.4 (d, 1H, 5-H(pyridinone)), 8.3 (d, 1H, 6-H(pyridinone)), 7.6-9.3 (br., 3H, OH)

Anal. Calcd. for C₇H₁₀NO₃Cl: C, 43.88; H, 5.26; N, 7.31%.

Found: C, 44.14;H, 5.34; N, 7.28%.

EXAMPLE 31 1,6-Dimethyl-2-hydroxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride

In an analogous hydrogenation procedure in the preparation of 1-methyl-2-hydroxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride, using 8-oxo-4,8-dihydro-2-phenyl-5,6-dimethyl-4H-pyridino[3,2-d]-m-dioxin (0.64 g, 2.5 mmol) and 5% Pd/C catalyst (0.1 g) yield the title compound 0.45 g (87.5%) after recrystallisation from methanol/diethyl ether, as a white crystalline solid. m.p. 140-143° C.

¹H-NMR (DMSO-d₆) δ: 2.7 (s, 3H, 6-CH₃), 4.06 (s, 3H, N—CH₃), 4.86 (s, 2H, 2-CH₂OH), 7.4 (s, 1H, 5-H(pyridinone)), 6.4-8.7 (br., 3H, OH)

Anal. Calcd. for C₈H₁₂NO₃Cl.1/2H₂O: C, 44.77; H, 6.10; N, 6.53%.

Found: C, 44.72; H, 6.00; N, 6.26%.

EXAMPLE 32 1,6-Dimethyl-2-(1-hydroxyethyl)-3-hydroxy-pyridin-4(1H)-one hydrochloride

In an analogous hydrogenation procedure in the preparation of 1-methyl-2-hydroxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride, using 8-oxo-4,8-dihydro-2-phenyl-4,5,6-trimethyl-4H-pyridino[3,2-d]-m-dioxin (1.36 g, 5 mmol) and 5% Pd/C catalyst (0.3 g) yield the title compound 0.9 g (82%) after recrystallisation from methanol/diethyl ether, as a light yellow crystalline solid. m.p. 208-212° C.

¹H-NMR (DMSO-d₆) δ: 1.4 (d, 3H, CHCH₃), 2.5 (s, 3H, 6-CH₃), 4.04 (s, 3H, N—CH₃), 5.65 (q, 1H, CHCH₃), 7.3 (s, 1H, 5-H(pyridinone)), 7.5-10.0 (br., 3H, OH)

Anal. Calcd. for C₉H₁₄NO₃Cl: C, 49.21; H, 6.42; N, 6.38%.

Found: C, 49.12; H, 6.33; N, 6.22%.

EXAMPLE 33 1,6-Dimethyl-2-(1-hydroxypropyl)-3-hydroxy-pyridin-4(1H)-one hydrochloride

In an analogous hydrogenation procedure in the preparation of 1-methyl-2-hydroxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride, using 8-oxo-4,8-dihydro-2-phenyl-4-ethyl-5,6-dimethyl-4H-pyridino[3,2-d]-m-dioxin (1.43 g, 5 mmol) and 5% Pd/C catalyst (0.3 g) yield the title compound 0.93 g (79.7%) after recrystallisation from methanol/diethyl ether, as a white crystalline solid. m.p. 221-223° C.

¹H-NMR (DMSO-d₆) δ: 0.8 (t, 3H, CHCH₂CH₃), 1.3-2.1 (m, 2H, CHCH₂CH₃), 2.43 (s, 3H, 6-CH₃), 3.94 (s, 3H, N—CH₃), 5.3 (t, 1H, CHCH₂CH₃), 7.15 (s, 1H, 5-H(pyridinone)), 7.5-10.5 (br., 3H, OH)

Anal. Calcd. for C₁₀H₁₆NO₃Cl: C, 51.40; H, 6.90; N, 5.99%.

Found: C, 51.45; H, 6.82; N, 5.89%.

EXAMPLE 34 1-Ethyl-2-(1-hydroxyethyl)-3-hydroxy-pyridin-4(1H)-one hydrochloride

In an analogous hydrogenation procedure in the preparation of 1-methyl-2-hydroxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride, using 8-oxo-4,8-dihydro-2-phenyl-4-methyl-5-ethyl-4H-pyridino[3,2-d]-m-dioxin (1.5 g, 5.5 mmol) and 5% Pd/C catalyst (0.3 g) yield the title compound 1.0 g (82.8%) after recrystallisation from methanol/diethyl ether, as a white crystalline solid. m.p. 139-140° C.

¹H-NMR (DMSO-d₆) δ: 1.3-1.9 (m, 6H, CHCH₃ & N—CH₂CH₃, 4.6 (q, 2H, N—CH₂CH₃), 5.55 (q, 1H, CHCH₃), 7.4 (d, 1H, 5-H(pyridinone)), 8.25 (d, 1H, 5-H(pyridinone)), 8.5-10.5 (br., 3H, OH)

Anal. Calcd. for C₉H₁₄NO₃Cl: C, 49.21; H, 6.42; N, 6.38%.

Found: C, 49.30; H, 6.44; N, 6.30%.

EXAMPLE 35 1-(3-hydroxypropyl)-2-hydroxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride

In an analogous hydrogenation procedure in the preparation of 1-methyl-2-hydroxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride, using 8-oxo-4,8-dihydro-2-phenyl-5-(3-hydroxypropyl)-4H-pyridino[3,2-d]-m-dioxin (1.44 g, 5 mmol) and 5% Pd/C catalyst (0.3 g) yield the title compound 0.98 g (83.2%) after recrystallisation from methanol/diethyl ether, as a white crystalline solid. m.p. 138-139° C.

¹H-NMR (D₂O) δ: 1.9-2.6 (m, 2H, N—CH₂CH₂CH₂O), 3.75 (t, 2H, N—CH₂CH₂CH₂O), 4.6 (m, 4H, N—CH₂CH₂CH₂O), 5.08 (s, 2H, CH₂O), 7.25 (d, 1H, 5-H(pyridinone)), 8.2 (d, 1H, 6-H(pyridinone))

Anal. Calcd. for C₉H₁₄NO₄Cl: C, 45.87; H, 5.99; N, 5.94%.

Found: C, 45.87; H, 6.02; N, 5.75%.

EXAMPLE 36 1-(3-hydroxypropyl)-2-(1-hydroxyethyl)-3-hydroxy-pyridin-4(1H)-one hydrochloride

In an analogous hydrogenation procedure in the preparation of 1-methyl-2-hydroxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride, using 8-oxo-4,8-dihydro-2-phenyl-4methyl-5-(3-hydroxypropyl)-4H-pyridino [3,2-d]-m-dioxin (1.3 g, 4.3 mmol) and 5% Pd/C catalyst (0.3 g) yield the title compound 0.88 g (82%) after recrystallisation from methanol/diethyl ether, as a yellow crystalline solid. m.p. 117-120° C.

¹H-NMR (DMSO-d₆) δ: 1.5 (d, 3H, CHCH₃), 1.65-2.45 (m, 2H, N—CH₂CH₂CH₂O), 3.45 (t, 2H, N—CH₂CH₂CH₂O), 4.65 (m, 4H, N—CH₂CH₂CH₂O), 5.5 (s, 2H, CHCH₃), 7.3 (d, 1H, 5-H(pyridinone)), 8.18 (d, 1H, 6-H(pyridinone)), 7.3-9.4 (br., 4H, OH)

Anal. Calcd. for C₁₀H₁₆NO₄Cl: C, 48.10; H, 6.46; N, 5.61%.

Found: C, 48.39; H, 6.32; N, 5.62%.

Orally Active Prodrug of the Invention

EXAMPLE 37 1-[(3-Benzoyloxy)propyl]-2-hydroxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride (Ester Prodrug of the Invention)

8-Oxo-4,8-dihydro-2-phenyl-5-[(3-benzoyloxy)propyl]-4H-pyridino [3,2-d]-m-dioxin (4.1 g, 10 mmol) was dissolved in 50 ml of DMF and adjusted to pH 1 with concentrated hydrochloric acid prior to hydrogenolysis for 6 hours in the presence of 5% Pd/C catalyst (1.0 g). Filtration followed by rotary evaporation in vacuo gave the crude product as a white solid. Recrystallization from methanoildiethyl ether gave the pure title compound (2.9 g, 85%) as a white crystalline solid. m.p. 142-143° C.

¹H-NMR (DMSO-d₆) δ: 1.9-2.8 (m, 2H, N—CH₂CH₂CH₂O), 4.0-5.0 (m, 4H, N—CH₂CH₂CH₂O), 4.8 (s, 2H, CH₂O), 7.2-8.1 (m, 6H, Ar & 5-H(pyridinone)), 8.3 (d, 1H, 6-H(pyridinone)), 8.5-10.2 (br., 3H, OH)

Anal. Calcd. for C₁₆H₁₈NO₅Cl: C, 56.56; H, 5.34; N, 4.12%.

Found: C, 56.40; H, 5.26; N, 4.08%.

De-Alkylated Active Metabolites of Orally Active Compounds of the Invention

EXAMPLE 38 1-Ethyl-2-hydroxymethyl-3-hydroxy-6-methyl-pyridin-4(1H)-one hydrochloride

1.3 g (4 mmol) 1-ethyl-2-methoxymethyl-3-benzyloxy-6-methyl-pyridin-4(1H)-one hydrochloride was added to 40 ml of 4N hydrochloric acid and refluxed for 6 hours. Concentration to dryness in vacuo afforded the crude product. Recrystallisation from methanol/diethyl ether gave the pure title compound (0.7 g, 80%) as a yellow crystalline solid. m.p. 160-162° C.

¹H-NMR (DMSO-d₆) δ: 1.3 (t, 3H, N—CH₂CH₃), 2.5 (s, 3H, 6-CH₃), 4.3 (q, 2H, N—CH₂CH₃), 4.6 (s, 2H, 2-CH₂O), 7.1 (s, 1H, 5-H(pyridinone)), 7.8-10.0 (br., 3H, OH)

Anal. Calcd. for C₉H₁₄NO₃Cl1/4H₂O: C, 48.22; H, 6.52; N, 6.25%.

Found: C, 48.44; H, 6.37; N, 6.15%.

EXAMPLE 39 1-Ethyl-2-hydroxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride

2.0 g (7.33 mmol) 1-ethyl-2-methoxymethyl-3-benzyloxy-pyridin-4(1H)-one was dissolved in 50 ml of 4N hydrochloric acid and refluxed for 6 hours. Concentration to dryness in vacuo afforded the crude product. Recrystallisation from methanol/diethyl ether gave the pure title compound (1.1 g, 73%) as a white crystalline solid. m.p. 168-169° C.

¹H-NMR (D₂O) δ: 1.45 (t, 3H, N—CH₂CH₃), 4.4 (q, 2H, N—CH₂CH₃), 4.88 (s, 2H, 2-CH₂O), 7.1 (d, 1H, 5-H(pyridinone)), 8.1 (d, 1H, 6-H(pyridinone))

Anal. Calcd. for C₈H₁₂NO₃Cl: C, 46.73; H, 5.88; N, 6.81%.

Found: C, 46.71; H, 5.97; N, 7.01%.

Orally Active Prodrugs of the Invention

EXAMPLE 40 1,6-Dimethyl-2-methoxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride

1,6-Dimethyl-2-methoxymethyl-3-benzyloxy-pyridin-4(1H)-one hydrochloride (1.55 g, 5 mmol) was dissolved in methanol (40 ml)/water (10 ml) and hydrogenated for 4 hours in the presence of 5% Pd/C (0.3 g). Following filtration the filtrate was concentrated in vacuo and the crude material recrystallised from methanol/diethyl ether gave the pure title compound (0.95 g, 86.5%) as a white crystalline solid. m.p. 156-159° C.

¹H-NMR (DMSO-d₆) δ: 2.53 (s, 3H, 6-CH₃), 3.28 (s, 3H, OCH₃), 3.83 (s, 3H, N—CH₃), 4.68 (s, 2H, 2-CH₂OCH₃), 7.25 (s, 1H, 5-H(pyridinone)), 6.0-8.5 (br., 2H, OH)

Anal. Calcd. for C₉H₁₄NO₃Cl: C, 49.21; H, 6.42; N, 6.38%.

Found: C, 49.33; H, 6.49; N, 6.16%.

EXAMPLE 41 1,6-Dimethyl-2-(1-methoxyethyl)-3-hydroxy-pyridin-4(1H)-one hydrochloride

In an analogous hydrogenation procedure in the preparation of 1,6-dimethyl-2-methoxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride using 1,6-dimethyl-2-(1-methoxyethyl)-3-benzyloxy-pyridin-4(1H)-one hydrochloride (1.62 g, 5 mmol) and 5% Pd/C catalyst (0.35 g) yield the title compound 1.06 g (90%) after recrystallisation from methanol/diethyl ether, as a white crystalline solid. m.p. 205-207° C.

¹H-NMR (DMSO-d₆) δ: 1.5 (d, 3H, CHCH₃), 2.56 (s, 3H, 6-CH₃), 3.24 (s, 3H, OCH₃),4.05 (s, 3H, N—CH₃), 5.4 (q, 1H, CHCH₃), 7.4 (s, 1H, 5-H(pyridinone)),8.5-10.0 (br., 2H, OH)

Anal. Calcd. for C₁₀H₁₆NO₃Cl: C, 51.40; H, 6.90; N, 5.99%.

Found: C, 51.61; H, 6.76; N, 5.89%.

EXAMPLE 42 1-Ethyl-2-methoxymethyl-3-hydroxy-6-methyl-pyridin-4(1H)-one hydrochloride

In an analogous hydrogenation procedure in the preparation of 1,6-dimethyl-2-methoxymethyl-3-hydroxy-pyridin-4(1H)-one hydrochloride using 1-ethyl-2-methoxymethyl-3-benzyloxy-6-methyl-pyridin-4(1H)-one hydrochloride (1.3 g, 4 mmol) and 5% Pd/C catalyst (0.3 g) yield the title compound 0.78 g (83%) after recrystallisation from methanol/diethyl ether, as a white crystalline solid. m.p. 174-176° C.

¹H-NMR (DMSO-d₆) δ: 1.47 (t, 3H, N—CH₂CH₃), 2.7 (s, 3H, 6-CH₃), 3.4 (s, 3H,OCH₃), 4.4 (q, 2H, N—CH₂CH₃), 4.76 (s, 2H, 2-CH₂OCH₃), 7.35 (s, 1H, 5-H(pyridinone))Anal.

Calcd. for C₁₀H₁₆NO₃Cl: C, 51.40; H, 6.90; N, 5.99%.

Found: C, 51.31; H, 7.11; N, 6.04%.

EXAMPLE 43 1,6-Dimethyl-2-(1-methoxypropyl)-3-hydroxy-pyridin-4(1H)-one hydrochloride

1,6-Dimethyl-2-(1-methoxypropyl)-3-benzyloxy-pyridin-4(1H)-one (1.65 g, 5.5 mmol) was dissolved in methanol (30 ml)/water (10 ml) and adjusted to pH 1 with concentrated hydrochloric acid prior to hydrogenolysis for 4 hours in the presence of 5% Pd/C catalyst (0.35 g). Filtration followed by rotary evaporation gave the crude product as a white solid. Recrystallization from methanol/diethyl ether gave the pure title compound (1.08 g, 79.3%) as a white crystalline solid. m.p. 225-227° C.

¹H-NMR (DMSO-d₆) δ: 0.9 (t, 3H, CHCH₂CH₃), 1.4-2.3 (m, 2H, CHCH₂CH₃), 2.6 (s, 3H, 6-CH₃), 3.28 (s, 3H, OCH₃), 4.04 (s, 3H, N—CH₃), 5.15 (t, 1H, CHCH₂CH₃), 7.4 (s, 1H, 5-H (pyridinone))

Anal. Calcd. for C₁₁H₁₈NO₃Cl: C, 53.33; H, 7.32; N, 5.65%.

Found: C, 53.30; H, 7.18; N, 5.56%.

EXAMPLE 44 1,6-Dimethyl-2-(1-ethoxyethyl)-3-hydroxy-pyridin-4(1H)-one hydrochloride

1,6-Dimethyl-2-(1-ethoxymethyl)-3-benzyloxy-pyridin-4(1H)-one (3.65 g, 12 mmol) was dissolved in 40 ml of ethanol and adjusted to pH 1 with concentrated hydrochloric acid prior to hydrogenolysis for 4 hours in the presence of 5% Pd/C catalyst (0.8 g). Filtration followed by rotary evaporation gave the crude product as a white solid. Recrystallization from ethanol/diethyl ether gave the pure title compound (2.48 g, 83.3%) as a white crystalline solid. m.p. 195-199° C.

¹H-NMR (CDCl₃) δ: 1.2 (t, 3H, OCH₂CH₃), 1.6 (d, 3H, CHCH₃), 2.65 (s, 3H, 6-CH₃), 3.5 (q, 2H, OCH₂CH₃), 4.1 (s, 3H, N—CH₃), 5.5 (q, 1H, CHCH₃), 7.4 (s, 1H, 5-H(pyridinone))

Anal. Calcd. for C₁₁H₁₈NO₃Cl: C, 53.33; H, 7.32; N, 5.65%.

Found: C, 53.46; H, 7.16; N, 5.56%.

Novel Intermediates for Synthesis of Amide Compounds of the Invention

EXAMPLE 45 2-Formyl-3-benzyloxy-6-methyl-pyran-4(1H)-one

To a solution of 2-hydroxymethyl-3-benzyloxy-6-methyl-pyran-4(1H)-one (5.28 g, 21.5 mmol, 1 eq) in 100 ml chloroform was added 27 ml of dimethyl sulfoxide and 18.5 ml of triethylamine and the reaction mixture was cooled with an ice-bath to an internal temperature of 3-5° C. Then sulfur trioxide pyridine complex (17.1 g 107 mmol, 5 eq) was added and the mixture was allowed to thaw to room temperature. After stirring for overnight at room temperature, the reaction mixture was washed with water (2×50 ml) and the organic phase was dried over Na₂SO₄, filtered and concentrated in vacuo to yield an organe oil. Further purification by column chromatography on silica gel (eluant: Et2O) furnished the pure product (4.6 g, 87.7%) as a white crystalline solid. m.p. 78-81° C.

¹H-NMR (CDCl₃) δ: 2.3 (s, 3H, 6-CH₃), 5.4 (s, 2H, CH₂Ph), 6.2 (s, 1H, 5-H(pyranone)), 7.28 (s, 5H, Ar), 9.75 (s, 1H, CHO)

Anal. Calcd. for C₁₄H₁₂O₄: C, 68.84; H, 4.95%. Found: C, 68.96; H, 5.07%.

EXAMPLE 46 2-Carboxy-3-benzyloxy-6-methyl-pyran-4(1H)-one

2-Formyl-3-benzyloxy-6-methyl-pyran-4(1H)-one (3.67 g, 15.03 mmol, 1 eq) was dissolved in acetone (50 ml) and the solution diluted with water (50 ml). To the reaction mixture was added sulfamic acid (2.04 g, 21.04 mmol, 1.4 eq) and 80% sodium chlorite (1.78 g, 15.8 mmol, 1.05 eq) and allowed to stir for 1 hour at room temperature in an open vessel. Removal of acetone in vacuo yielded crude product as a precipitate in the remaining aqueous solution. The solid was collected, washed with absolute ethanol and dried (3.32 g, 85%). m.p. 173-175° C.

¹H-NMR (DMSO-d₆) δ: 2.32 (s, 3H, 6-CH₃), 5.18 (s, 2H, CH₂Ph), 6.2 (s, 1H, 5-H(pyranone)), 7.1-7.6 (m, 5H, Ar)

Anal. Calcd. for C₁₄H₁₂O₅: C, 64.6; H, 4.6%. Found: C, 64.7; H, 4.9%.

EXAMPLE 47 3-(2-Carbonyl-3-benzyloxy-6-methyl-4(1H)-pyran-2-yl)-1,3-thiazolidine-2-thione

2-Carboxy-3-benzyloxy-6-methyl-pyran-4(1H)-one (2.78 g, 10 mmol, 1 eq) was dissolved in 100 ml dichloromethane and the solution stirred vigorously. Dicyclohexylcarbodiimide (DCCI) (2.3 g, 11 mmol, 1.1 eq) was then added followed by the addition of 2-mercaptothiazoline (1.32 g, 11 mmol, 1.1 eq) and a catalytic amount of 4-dimethylaminopyridine (DMAP) (50 mg). The mixture was stirred for 24 h, the white precipitate N,N′-dicyclohexylurea (DCU) filtered from the yellow solution and the filtrate volume was adjusted to 200 ml with CH₂Cl₂. The dichloromethane layer was washed with 3×100 ml 0.1N sodium hydroxide solution, 100 ml water, dried (Na₂SO₄), and concentrated in vacuo to yield the crude product as a yellow oil. Further purification by column chromatography on silica gel (eluant: EtOAc) furnished the pure product as a bright yellow oil (2.56 g, 71%).

¹H-NMR (CDCl₃) δ: 2.28 (s, 3H, 6-CH₃), 3.1 (t, 2H, CH₂N), 4.35 (t, 2H, CH₂S), 5.3 (s, 2H, CH₂Ph), 6.25 (s, 1H, 5-H(pyranone)), 7.28 (s, 5H, Ar)

Anal. Calcd. for C₁₇H₁₅NO₄S₂: C, 56.49; H, 4.18%. Found: C, 56.98; H, 4.52%.

EXAMPLE 48 3-Benzyloxy-6-methyl-4(1H)-pyranone-2-carboxy-(N-methyl)-amide

To a solution of 3-(2-carbonyl-3-benzyloxy-6-methyl-4(1H)-pyran-2-yl)-1,3-thiazolidine-2-thione (3.61 g, 10 mmol, 1 eq) in 100 ml dichloromethane wad added 10 ml (20 mmol, 2 eq.) of 2M methylamine in THF and the reaction mixture allowed to stir for 2 h. The dichloromethane layer was washed with 3×50 ml 0.1N sodium hydroxide solution, 50 ml water, dried (Na₂SO₄), and the solvent removed in vacuo. The crude product was further purified by column chromatography on silica gel (eluant: EtOAc) furnished the pure product as a light yellow oil (2.4 g, 88%).

¹H-NMR (CDCl₃) δ: 2.3 (s, 3H, 6-CH₃), 2.7 (d, 3H, CH₃NH), 5.28 (s, 2H, CH₂Ph), 6.27 (s, 1H, 5-H (pyranone)), 7.3 (s, 5H, Ar)

EXAMPLE 49 3-Benzyloxy-6-methyl-4(1H)-pyranone-2-carboxy-(N-isopropyl)-amide

In an analogous procedure in the preparation of 3-benzyloxy-6-methyl-4(1H)-pyranone-2-carboxy-(N-methyl)-amide using isopropylamine (1.5 eq) yielded the title compound as a yellow oil. Further purification by column chromatography on silica gel (eluant: EtOAc) furnished the pure product as a light yellow oil (yield 88%).

¹H-NMR (CDCl₃) δ: 1.0 (d, 6H, CH(CH₃)₂), 2.4 (s, 3H, 6-CH₃), 3.7-4.5 (m, 1H, CHNH), 5.4 (s, 2H, CH₂Ph), 6.25 (s, 1H, 5-H(pyranone)), 7.4 (s, 5H, Ar)

EXAMPLE 50 3-Benzyloxy-6-methyl-4(1H)-pyranone-2-carboxy-(N-2′-methoxyethyl)-amide

In an analogous procedure in the preparation of 3-benzyloxy-6-methyl-4(1H)-pyranone-2-carboxy-(N-methyl)-amide using 2-methoxyethylamine (1.5 eq) yielded the title compound after purification by column chromatography on silica gel (eluant: EtOAc) as a light yellow oil (yield 94%).

¹H-NMR (CDCl₃) δ: 2.25 (s, 3H, 6-CH₃), 3.2 (s, 3H, OCH₃), 3.0-3.6 (m, 4H, CH₂CH₂), 5.28 (s, 2H, CH₂Ph), 6.1 (s, 1H, 5-H(pyranone)), 7.26 (s, 5H, Ar), 7.5-8.2 (br., 1H, NH)

EXAMPLE 51 3-Benzyloxy-6-methyl-4(1H)-pyranone-2-carboxy-(N-2′-hydroxyethyl)-amide

In an analogous procedure in the preparation of 3-benzyloxy-6-methyl-4(1H)-pyranone-2-carboxy-(N-methyl)-amide using 2-hydroxyethylamine (1.5 eq) yielded the title compound after purification by column chromatography on silica gel (eluant: EtOAc) as a light yellow oil (yield 90%).

¹H-NMR (CDCl₃) δ: 2.3 (s, 3H, 6-CH₃), 3.1-3.8 (m, 4H, CH₂CH₂), 5.29 (s, 2H, CH₂Ph), 6.15 (s, 1H, 5-H(pyranone)), 7.3 (s, 5H, Ar), 7.5-8.2 (br., 1H, NH)

EXAMPLE 52 3-benzyloxy-6-methyl-4(1H)-pyranone-2-carboxy-(N,N-dimethyl)-amide

In an analogous procedure in the preparation of 3-benzyloxy-6-methyl-4(1H)-pyranone-2-carboxy-(N-methyl)-amide using 2M dimethylamine in THF (3 eq) yielded the title compound after purification by column chromatography on silica gel (eluant: EtOAc) as a light yellow oil (yield 88%).

¹H-NMR (CDCl₃) δ: 2.31 (s, 3H, 6-CH₃), 2.88 (s, 3H, CH₃N), 3.03 (s, 3H, CH₃N), 5.2 (s, 2H, CH₂Ph), 6.22 (s, 1H, 5-H(pyranone)), 7.35 (s, 5H, Ar)

Orally Active Prodrugs of the Invention

EXAMPLE 53 1,6-Dimethyl-3-benzyloxy-4(1H)-pyridinone -2-carboxy-(N-methyl)-amide

To a solution of 3-benzyloxy-6-methyl-4(1H)-pyranone-2-carboxy-(N-methyl)-amide (1.37 g, 5 mmol, 1 eq.) in methanol (10 ml) was added 20 ml (40 mmol, 8 eq.) of 2M methylamine in methanol. The reaction mixture was sealed in a thick-walled glass tube and stirred at 70° C. for 12 hours. After removal of the solvent, the residue was purified by column chromatography on silica gel (eluant: 12% CH₃OH/88% CHCl₃) furnished the pure product (1.1 g, 76.9%) as a white crystalline solid. m.p. 164-165.5° C.

¹H-NMR (CDCl₃) δ: 2.2 (s, 3H, 6-CH₃), 2.65 (d, 3H, CH₃NH), 3.47 (s, 3H, N—CH₃), 4.92 (s, 2H, CH₂Ph), 5.95 (s, 1H, 5-H(pyridinone)), 7.28 (s, 5H, Ar), 7.9-8.4 (br, 1H, NH)

EXAMPLE 54 1,6-Dimethyl-3-benzyloxy-4(1H)-pyridinone -2carboxy-(N-isopropyl)-amide

In an analogous procedure in the preparation of 1,6-dimethyl-3-benzyloxy-4(1H)-pyridinone-2-carboxy-(N-methyl)-amide using 1,6-dimethyl-3-benzyloxy-4(1H)-pyridinone-2-carboxy-(N-isopropyl)-amide yielded the crude product. Further purification by column chromatography on silica gel (eluant: 10% CH₃OH/90% CHCl₃) afforded the pure title compound as a pale yellow crystalline solid (yield, 79%) m.p. 176-178° C.

¹H-NMR (CDCl₃) δ: 1.2 (d, 6H, CH(CH₃)₂), 2.1 (s, 3H, 6-CH₃), 3.48 (s, 3H, N—CH₃), 3.9-4.5 (m, 1H, CHNH), 4.98 (s, 2H, CH₂Ph), 5.98 (s, 1H, 5-H(pyridinone)), 7.22 (s, 5H, Ar), 8.0-8.4 (br, 1H, NH)

EXAMPLE 55 1,6-Dimethyl-3-benzyloxy-4(1H)-pyridinone -2-carboxy-(N-2′-methoxyethyl)-amide

In an analogous procedure in the preparation of 1,6-dimethyl-3-benzyloxy-4(1H)-pyridinone-2-carboxy-(N-methyl)-amide using 1,6-dimethyl-3-benzyloxy-4(1H)-pyridinone-2-carboxy-(N-2′-methoxyethyl)-amide yielded the pure title compound after purification by column chromatography on silica gel (eluant: 10% CH₃OH/90% CHCl₃) afforded as a white crystalline solid (yield, 82%) m.p. 125-126° C.

¹H-NMR (CDCl₃) δ: 2.1 (s, 3H, 6-CH₃), 3.2 (s, 3H, OCH₃), 3.1-3.7 (m, 4H, CH₂CH₂), 3.42 (s, 3H, N—CH₃), 4.95 (s, 2H, CH₂Ph), 6.02 (s, 1H, 5-H(pyridinone)), 7.0-7.5 (m, 5H, Ar), 7.8-8.4 (br, 1H, NH)

EXAMPLE 56 1,6-Dimethyl-3-benzyloxy-4(1H)-pyridinone -2-carboxy-( N-2′-hydroxyethyl)-amide

In an analogous procedure in the preparation of 1,6-dirnethyl-3-benzyloxy-4(1H)-pyridinone-2-carboxy-(N-methyl)-amide using 1,6-dimethyl-3-benzyloxy-4(1H)-pyridinone-2-carboxy-(N-2′-hydroxyethyl)-amide yielded the pure title compound after purification by column chromatography on silica gel (eluant: 15% CH₃OH/85% CHCl₃) afforded as a white crystalline solid (yield, 86%) m.p. 153-155° C.

¹H-NMR (CDCl₃) δ: 2.1 (s, 3H, 6-CH₃), 3.1-3.7 (m, 4H, CH₂CH₂), 3.42 (s, 3H, N—CH₃), 4.95 (s, 2H, CH₂Ph), 6.02 (s, 1H, 5-H(pyridinone)), 7.0-7.5 (m, 5H, Ar), 7.8-8.4 (br, 1H, NH)

EXAMPLE 57 1,6-Dimethyl-3-benzyloxy-4(1H)-pyridinone -2-carboxy-( N,N-dimethyl)-amide

In an analogous procedure in the preparation of 1,6-dimethyl-3-benzyloxy-4(1H)-pyridinone-2-carboxy-(N-methyl)-amide using 1,6-dimethyl-3-benzyloxy-4(1H)-pyridinone-2-carboxy-(N,N-dimethyl)-amide yielded the pure title compound after purification by column chromatography on silica gel (eluant: 10% CH₃OH/90% CHCl₃) afforded as a yellow oil (yield, 46%)

¹H-NMR (CDCl₃) δ: 2.3 (s, 3H, 6-CH₃), 2.8 (s, 3H, CH₃N), 3.0 (s, 3H, CH₃N), 3.42 (s, 3H, N—CH₃), 5.2 (q, 2H, CH₂Ph, AB center), 6.3 (s, 1H, 5-H(pyridinone)), 7.0-7.5 (m, 5H, Ar)

EXAMPLE 58 1,6-Dimethyl-3-hydroxy-4(1H)-pyridinone-2-carboxy-(N-methyl)-amide hydrochloride

0.86 g of 1,6-dimethyl-3-benzyloxy-4(1H)-pyridinone-2-carboxy-(N-methyl)-amide was dissolved in 30 ml of DMF and hydrogenated at room temperature for 3 hours in the presence of 5% Pd/C catalyst (0.2 g). The catalyst was removed by filtration and the filtrate was acidified to pH 1 with concentrated hydrochloric acid followed by rotary evaporation in vacuo gave the crude product as a white solid. Recrystallization from methanol/diethyl ether gave the pure title compound (0.65 g, 93%) as a white crystalline solid. m.p. 238° C. (dec.)

¹H-NMR (DMSO-d₆) δ: 2.5 (s, 3H, 6-CH₃), 2.7 (d, 3H, CH₃NH), 3.7 (s, 3H, N—CH₃), 7.2 (s, 1H, 5-H(pyridinone)), 6.8-8.1 (br, 2H, OH), 8.7-9.2 (br, 1H, NH)

Anal. Calcd. for C₉H₁₃ClN₂O₃: C, 46.42; H, 5.59; N, 12.03% Found: C, 46.28; H, 5.71; N, 11.86%.

EXAMPLE 59 1,6-Dimethyl-3-hydroxy-4(1H)-pyridinone -2-carboxy-(N-isopropyl)-amide hydrochloride

An analogous hydrogenation procedure to the preparation of 1,6-dimethyl-3-hydroxy-4(1H)-pyridinone-2-carboxy-(N-methyl)-amide hydrochloride, using 1,6-dimethyl-3-benzyloxy-4(1H)-pyridinone-2 carboxy-(N-isopropyl)-amide and 5% Pd/C catalyst yielded the title compound (yield, 93%) after recrystallisation from methanol/diethyl ether, as a white crystalline solid. m.p. 219-220° C.

¹H-NMR (DMSO-d₆) δ: 1.18 (d, 6H, CH(CH₃)₂), 2.52 (s, 3H, 6-CH₃), 3.7 (s, 3H, N—CH₃), 3.6-4.4 (m, 1H, CHNH), 5.2-6.5 (br, OH), 7.3 (s, 1H, 5-H(pyridinone)), 8.8-9.2 (br, 1H, NH) Anal. Calcd. for C₁₁H₁₇ClN₂O₃: C, 50.63; H, 6.52; N, 10.74% Found: C, 50.38; H, 6.81; N, 10.56%.

EXAMPLE 60 1,6-Dimethyl-3-hydroxy-4(1H)-pyridinone-2-carboxy-(N-2′-methoxyethyl)-amide hydrochloride

An analogous hydrogenation procedure to the preparation of 1,6-dimethyl-3-hydroxy-4(1H)-pyridinone-2-carboxy-(N-methyl)-amide hydrochloride, using 1,6-dimethyl-3-benzyloxy-4(1H)-pyridinone-2-carboxy-(N-2′-methoxyethyl)-amide yielded the title compound-(yield, 90%) after recrystallisation from methanol/diethyl ether, as a white crystalline solid. m.p. 204-206° C.

¹H-NMR (DMSO-d₆) δ: 2.6 (s, 3H, 6-CH₃), 3.4 (s, 3H, OCH₃), 3.1-3.6 (m, 4H, CH₂CH₂), 3.8 (s, 3H, N—CH₃), 7.35 (s, 1H, 5-H(pyridinone)), 8.8-10.05 (br, OH & NH)

Anal. Calcd. for C₁₁H₁₇ClN₂O₄: C, 47.70; H, 6.14; N, 10.12% Found: C, 47.56; H, 6.30; N, 10.36%.

EXAMPLE 61 1,6-Dimethyl-3-hydroxy-4(1H)-pyridinone-2-carboxy-(N-2′-hydroxyethyl)-amide hydrochloride

An analogous hydrogenation procedure to the preparation of 1,6-dimethyl-3-hydroxy-4(1H)-pyridinone-2-carboxy-(N-methyl)-amide hydrochloride, using 1,6-dimethyl-3-benzyloxy-4(1H)-pyridinone-2-carboxy-(N-2′-hydroxyethyl)-amide yielded the title compound (yield, 91%) after recrystallisation from methanol/diethyl ether, as a white crystalline solid. m.p. 178-181° C.

¹H-NMR (DMSO-d₆) δ: 2.55 (s, 3H, 6-CH₃), 3.1-3.7 (m, 4H, CH₂CH₂), 3.85 (s, 3H, N—CH₃), 7.25 (s, 1H, 5-H(pyridinone)), 6.7-8.2 (br., OH), 9.1 (t, 1H, NH)

Anal. Calcd. for C₁₀H₁₅ClN₂O₄: C, 45.68; H, 5.71; N, 10.66% Found: C, 45.47; H, 5.98; N, 10.48%.

EXAMPLE 62 1,6-Dimethyl-3-hydroxy-4(1H)-pyridinone -2-carboxy-(N,N-dimethyl)-amide hydrochloride

An analogous hydrogenation procedure to the preparation of 1,6-dimethyl-3-hydroxy-4(1H)-pyridinone-2-carboxy-(N-methyl)-amide hydrochloride, using 1,6-dimethyl-3-benzyloxy-4(1H)-pyridinone-2-carboxy-(N,N-dimethyl)-amide yielded the title compound (yield, 94%) after recrystallisation from methanol/diethyl ether, as a white crystalline solid. m.p. 219° C.(dec.)

¹H-NMR (DMSO-d₆) δ: 2.5 (s, 3H, 6-CH₃), 2.8 (s, 3H, CH₃N), 3.0 (s, 3H, CH₃N), 3.65 (s, 3H, N—CH₃), 7.25 (s, 1H, 5-H(pyridinone)), 7.5-9.0 (br., OH)

Anal. Calcd. for C₁₀H₁₅ClN₂O₃: C, 48.64; H, 6.08; N, 11.35% Found: C, 48.58; H, 6.22; N, 11.08%.

EXAMPLE 63 Formulation of Medicaments

(A) Tablets of the following composition are prepared:

mg/tablet Compound of formula (I) (micronised) 250 ‘Avicel’ (microcrystalline cellulose) 38 polyvinylpyrrolidone 3 alginic acid 6 magnesium stearate 3

The 3-hydroxypyridin-4-one is mixed with ‘Avicel’ and polyvinylpyrrolidone is added, dissolved in sufficient industrial methylated spirits (74° OP) to produce a mass suitable for granulating. The mass is granulated through a 20 mesh sieve and the resultant granules are dried at a temperature not exceeding 50° C. The dried granules are passed through a 20 mesh sieve and the alginic acid and magnesium stearate. are then added and mixed with the granules. The product is compressed into tablets each weighing 300 mg on ⅜ inch flat bevelled edge divided punches

(B) Tablets of the following composition are prepared:

mg/tablet Compound of formula (I) (micronised) 250 ‘Avicel’ (microcrystalline cellulose) 134 polyvinylpyrrolidone 4 alginic acid 8 magnesium stearate 4

The tablets are prepared by essentially the same procedure as described in (A) and are compressed at a tablet weight of 400 mg on {fraction (7/16)} inch flat bevelled edge punches.C)

Tablets of the following composition are prepared:

mg/tablet Compound of formula (I)(micronised) 250 lactose (300 mesh) 19 maize starch 15 gelatine 10 magnesium stearate 6

The 3-hydroxypyridin-4-one is mixed with lactose and half the total quantity of maize starch required, and a 5% solution of gelatine in water is added to the mass. The product is granulated through a 16 mesh sieve, and the resultant granules are dried to constant weight at a temperature not exceeding 50° C. The dried granules are passed through a 20 mesh sieve and mixed with magnesium stearate and the remainder of the maize starch. The product is compressed at a 300 mg tablet weight on ⅜ inch flat bevelled edge divided punches.

EXAMPLE 64 Iron III Mobilisation Efficacy Assay in Rat: Oral Administration

Hepatocytes of manually fasted rats (190-230 g) were labelled with 10 μg ⁵⁹Fe ferritin injected iv into the tail vein. One hour later each rat was administered orally with a dose of chelator (150-450 μmol/Kg: see Table 2 below). Control rats were given an equivalent volume of water. The rats were placed in individual metabolic cages and their urine and faeces collected. One hour after the administration they were allowed access to food, with no restriction on water being made throughout the study period. The investigation was terminated 24 hours after the ⁵⁹Fe ferritin administration when rats were sacrificed and their livers and gastrointestinal tracts, including all contents including faeces, were removed for gamma counting. Iron mobilisation efficiency is shown in Tables 1 to 3

TABLE 1 pM Iron Mobilisation Compound Structure D _(pH 7.4) pKa Logβ₃ _(pH 7.45) (%) CP20*

0.17 3.56, 9.64 (s) 3.68, 9.77 (p) 36.3 19.4 10.7 ± 3.0% (n = 10) CP94*

1.79 3.81, 9.93 (p) 36.7 19.7 58.3 ± 9.4% (n = 10) CP41*

0.13 — — — 29.9 ± 4.3% (n = 5) CP359

0.14 2.88, 9.05 (s) 2.80, 9.27 (p) 35.25 20.96 33.3 ± 6.7% (n = 5) CP360

0.098 3.37, 9.42 (s) 3.32, 9.44 (p) 35.51 20.43  4.5 ± 1.1% (n = 5) CP361

0.25 3.55, 8.97 (s) 3.54, 8.99 (p) 35.52 21.47 48.4 ± 7.2% (n = 10) CP362

0.42 — — — 51.5 ± 3.7% (n = 5) CP363

1.09 3.22, 9.43 (s) 3.20, 9.44 (p) — — 73.5 ± 8.1% (n = 10) CP364

0.048 2.93, 9.12 (s) 3.13, 9.22 (p) 35.3 20.75 8.44 ± 3.6% (n = 5) CP365

0.27 3.11, 8.74 (s) 3.03, 8.77 (p) 34.8 21.3 54.5 ± 9.9% (n = 5) CP366

0.056 2.87, 9.14 (s) 3.02, 9.29 (p) 35.25 20.69 11.7 ± 4.1% (n = 5) CP367

5.61 2.70, 8.95 (s) 2.60, 9.07 (p) — — 56.0 ± 6.0% (n = 10) CP369

0.223 3.28, 9.38 (s) 3.29, 9.45 (p) 35.6 20.35 12.9 ± 2.3% (n = 5) CP370

1.08 — — — 41.6 ± 7.5% (n = 5) CP372

0.075 2.96, 8.69 (s) 2.98, 8.72 (p) 34.67 21.48 14.3 ± 4.5% (n = 5) CP373

3.32 — — — 39.5 ± 4.8% (n = 5) CP374

0.73 2.78, 8.98 (s) 2.76, 9.00 (p) 35.03 20.95  60.4 ± 15.6% (n = 5) CP375

3.85 — — — 72.0 ± 8.2% (n = 5) * = Comparative example of prior art

TABLE 2 Efficacy studies with different doses Dose Iron Effi- Chela- (μmol/ Mobilisation cacy tor Structure kg) (%) (%) Control — — 3.87 ± 1.0 — CP20*

450 300 150 13.4 ± 5.2  9.2 ± 2.2  6.3 ± 2.1  9.5  5.4  2.4 CP94*

450 300 150  59.7 ± 10.9 35.7 ± 4.4 16.5 ± 6.2 55.8 31.8 12.6 CP363

450 300 150 73.5 ± 8.1 66.9 ± 8.7 (n = 5) 40.7 ± 2.4 (n = 5) 69.6 63.0 36.8 CP374

450 150  60.4 ± 15.6 34.0 ± 4.3 (n = 5) 56.5 30.1 CP375

450 150 72.0 = 8.2 40.2 ± 8.5 (n = 5) 68.1 36.3 * = Comparative Examples of prior art compounds

TABLE 3 pM Iron Mobilisation Compd Structure D _(pH 7.4) PKa Logβ₃ _(pH 7.45) (%) CP502

0.04 2.64, 8.36 (s) 2.83, 8.38 (p) 35.78 23.42 62.4 ± 5.0% (n = 5) CP504

0.30 2.64, 8.56 (s) 2.81, 8.74 (p) 35.34 22.46 45.8 ± 6.1% (n = 5) CP506

0.04 2.50, 8.35 (s) 2.62, 8.34 (p) 34.88 22.57 40.9 ± 7.1% (n = 5) CP507

0.02 2.57, 8.19 (s) 2.65, 8.28 (p) 34.63 22.73 29.2 ± 6.3% (n = 5) CP508

0.16 2.61, 8.10 (s) 2.61, 8.10 (p) 35.13 23.46 35.0 ± 9.8% (n = 5) Novartis bidentate ligand (3)*

2.81 2.60, 8.39 (s) 2.59, 8.38 (p) 35.57 23.15  50.8 ± 10.3% (n = 5) 

What is claimed is:
 1. An 8-oxo-4,8-dihydro-2-phenyl-4H[3,2-d]-m-dioxin of formula (IIb),

wherein R³ is selected from the group consisting of hydrogen and C₁₋₆ alkyl; R⁴ is selected from the group consisting of hydrogen, C₁₋₆ alkyl, —CR⁶R⁶OR⁷, —CONH—R⁵, —CONHCOR⁵ and —CON(C_(n)H_(2n+1))₂; R⁵ is selected from the group consisting of hydrogen and optionally hydroxy, alkoxy, aryloxy substituted C₁₋₁₃ alkyl, aralkoxy substituted C₁₋₁₃ alkyl, aryl and C₇₋₁₃ aralkyl; R⁶ is independently selected at each occurrence from the group consisting of hydrogen, C₁₋₁₃ alkyl, aryl and C₇₋₁₃ aralkyl; R⁷ is selected from the group consisting of hydrogen, C₁₋₁₃ alkyl, aryl and C₇₋₁₃ aralkyl; (C_(n)H_(2n+1))₂ is selected from the group consisting of C₁₋₆ alkyl; and R₁₀ is selected from the group consisting of hydrogen and C₁₋₁₃ alkyl; and excluding 6-hydroxy methyl-2-phenyl-pyrano[3,2-d]-1,3-dioxin-8(4H)-one. 